Can someone explain me where this 13 came from, ? (sorry my poor english i'm brazilian)
a-7=3(b+2)
a=3(b+2)+7
a=3b+13

Hey there,

a-7=3(b+2), we do 3 times b and 3 times 2 according to the rule.

a-7=3b+6 we change + to - and - to + when move nums from 1 side to another one.

a=3b+13 we get the solution.

Hope this helps :)

step-by-step explanation:

y = | -2(-2) |     →     y = | 4 |     →     y = 4       ⇒   (-2, 4)

y = | -2(-1) |     →     y = | 2 |     →       y =   2       ⇒   (-1, 2)    

y = | -2(0) |     →     y = | 0 |     →       y = 0         ⇒   (0, 0)

y = | -2(1) |   c →     y = | -2 |     →     y =   2         ⇒   (1, 2)    

y = | -2(2) |     →     y = | - 4 |     →     y =   4         ⇒   (2, 4)