algebra
posted by tiffany .
solve the system of equations using substitution.
y = x + 10
y = 3x
a. (5, 15)
b. (2.5, 7.5)
c. (–15, –5)
d. (–5, –15)

3x = x + 10
Solve for x, then put that value in the second equation (above) to find y. Put both in the first equation to check.