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a + 3b = 12, a = 12 - 3b

3(12-3b) + b = 20

36-9b + b = 20

36-8b = 20

8b = 16

b = 2

2a + 12 = 24

2a = 12

a = 6

x^2 - 8x - 20

(x - 10)(x+2)

(Explanation and helping understanding) Remember the last 2 numbers must multiply to equal the last number in the question and add together to equal the middle nu...

To begin answering this question create a small grid

put 5 on the left hand side and put 2x and -6 seperately at the top of the grid

then you can multiply 5 by 2x to gain 10x and multiply 5 ...

Distance = 4 x 85 = 340km

Average speed = 340 / 5 = 68 km/h

So this question wants you to rearrange the formula so that b is on its own on one side of the equals sign. As its a formula and not asking for the value of the equation you don't have to worry about solv...