Solve the system of equations by substitution. X + Y=40 Y=9X

Answer 1

We can solve this by substitution.

Because Y = 9X, we can substitute 9X in for Y in the second equation.

X + Y = 40 becomes X + (9X) = 40

This becomes 10X = 40 so X = 4.

Plug 4 in for X in one of the equations and solve for Y

Answer 2

x + y = 40

y = 9x

x + 9x = 40 (substitute 9x for y in 1st equation)

10 x = 40

x = 4

4 + y = 40 (substitute 4 for x in 1st equation)

y = 36