what is the subsitution for 3y – 8x = 1 and y -4x = 7

Answer 1

To solve by substitution, one of the equations should be solved for one of the variables. The easiest equation to modify is the second equation.

y - 4x = 7 given second equation

y = 4x + 7 solved for y

3y - 8x = 1 given first equation

3(4x + 7) - 8x = 1

12x + 21 - 8x = 1

4x + 21 = 1

4x = -20

x = -5

y = 4x + 7

y = 4(-5) + 7

y = -20 + 7

y = -13