У = 6x - b

-3 х + 1/2y = - 3

You have to use the subsitution method

Step-by-step explanation:

so it's telling you what the y value is an you have to subsitute 6x-b where the y is.

so the new eqaution would be - 3x+1/2 (6x-b) = -3

-3x+3x-b=-3

-b=-3

b=3

the b is the in y=x+b