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You know the following: 
A) 80, 10%
B) 75, 20%
C) 50, 45%
D) 90, 5%
E) X, (100-10-20-45-5)% = 20%
Therefore, create a formula with the facts given and the mean marks must be ...

To solve a quadratic equation we need to find the value of x for which ax²+bx+c=0,where a,b,c are constants.There are some well known formulas which you should get accustomed with.Howe...

 The problem is:
‘Tom travels from a to b and at a speed of 90km per hour. It takes him time ‘t’. Alice travels from a to b at a speed of 70km per hour. It takes her time ‘t+ 1 hour’.
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There is a simple way of making calculations with percentages.
Say you want to subtract from a numerical value x,20%. Then multiply it with 80/100.
Say you want to add 20%.Then multiply with 120...

Many students ask how they can they find 2 unknowns,given 2 simple equations. I'll try to focus in this answer on giving students a tool which they can use to solve ANY 2 simple equations with one solutio...