sounds as if you know you need two equations for two unknowns! Good!!!
x + y = 70 That's the first equation.
x - 16 = y That's the second equation.
Using the second equation for substitution into the first equation, get:
x + y = 70 or x + x - 16 = 70
Solve for x:
2x = 86
x = 43 and y =27