Solve for x and y using these simultaneous equations: 2x + 3y = 21, y = 2x - 1

Substitute y = 2x - 1 into the first equation.

2x + 3(2x -1) = 21

2x + 6x - 3 = 21

8x = 24

x = 3

Therefore y = 2(3) - 1 = 5