How do you solve y equals 2x plus 15 and y equals 4x plus 7 using substitution?

y = 2x + 15

y = 4x + 7

Substitute the value of y from the first equation into the second:

2x + 15 = 4x + 7

Subtract 2x from both sides: 15 = 2x + 7

Subtract 7 from both sides: 8 = 2x

Divide both sides by 2: 4 = x.

Replace x by its value, 4, in the first equation:

y = 2*4 + 15 = 8 + 15 = 23

So the solution is (x, y) = (4, 23)