Question

B = -1-7ab=−1−7a I need help with this question

Answer 1

b = -1-7ab=−1−7a

Can be rewritten to be easier to understand.

$b = -1-7ab\\-1 -7a = -1-7ab$

In addition you can say the following equation is valid due to the way your problem was given to you.

$b = -1-7a$

Of course, you can simplify equation 2

$-1-7a = -1-7ab\\-7a = -7ab\\a = ab\\1 = b\\b = 1$

This ends up giving you b so you don't end up having to do any substitution in order to find b. Now substitute the value for b into either equation. I'm choosing the third because it's easiest.

$b = -1-7a$

$1 = -1 -7a\\2 = -7a\\-\frac{2}{7} = a\\a = -\frac{2}{7}$

And there you go :)