MYTUTOR SUBJECT ANSWERS

355 views

Solve the following simultaneous equation: 3x+2y=20 and x+4y=20

In this example, we want to find values for both x and y which are our unknowns. 

So we start by rearranging x to be on its own but still in terms of y. We then can plot it into the next equation. 

Hence we get the following equations:

.  x=20-4y (See, 4y has been taken over to the other side and hence the sign changes)

.  3x+2y=20

Then we substitute this new value of x in the other equation:

3(20-4y)+2y=20

60-12y+2y=20 (we have multiplied out the 3 and its bracket to simplify)

-10y=20-60 (make sure you change the sign when taking the 60 across!)

-10y=-40

-y=-4 (here we divided 40 by 10)

y=4 (the minus signs cancel each other out)

Now that you've found y we must plot it back into the original equation to find x:

x+4y=20

x+4(4)=20

x+16=20

x=20-16

x=4

Therefore, x=4 and y=4.

Phillipa S. 13 Plus  Maths tutor

7 months ago

Answered by Phillipa, a 13 Plus Maths tutor with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

206 SUBJECT SPECIALISTS

£18 /hr

Ana S.

Degree: Physics (Bachelors) - Oxford, Balliol College University

Subjects offered:Maths, Physics+ 3 more

Maths
Physics
.STEP.
.PAT.
-Oxbridge Preparation-

“A friendly and understanding tutor with three years experience in school clubs, summer camps and private tutoring.”

£18 /hr

Bryony S.

Degree: Economics (Bachelors) - Exeter University

Subjects offered:Maths, French

Maths
French

“Exams shouldn't be the cause of stress. Tutors should be there to reassure tutees and give them positive feedback.”

£18 /hr

Quentin D.

Degree: Structural Engineering with Architecture (Bachelors) - Edinburgh University

Subjects offered:Maths, Science+ 2 more

Maths
Science
Physics
French

“Hello! My name is Quentin Dorleans and I am a french IB graduate currently in my first year of studying Engineering at the University of Edinburgh. I am not a big study fan, and being extremely sporty myself I totally understand those ...”

About the author

£18 /hr

Phillipa S.

Degree: Engineering (Masters) - Exeter University

Subjects offered:Maths

Maths

“About me: Hello guys! I'm Phillipa and am currently in my second year at Exeter University doing Civil and Environmental Engineering. So maths maths maths. Super keen on tutoring, I worked with kids aged 13 and 15 with their homewo...”

MyTutor guarantee

You may also like...

Other 13 Plus Maths questions

Solve the following simultaneous equation: 3x+2y=20 and x+4y=20

Solve 0.5(6d+2)-4=10

How do I work out the area of different shapes?

What is the median, upper quartile and lower quatile. How do we find them?

View 13 Plus Maths tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok