Carcass wrote:
If m - n = 5 and 2m + 3n = 15, then m+n =
A 1
B 6
C 7
D 10
E 15
Note: The question is not asking us to find the individual values of m and n. So we need not solve the entire system. We need only find the value of m+nWe are given the following system of equations:
m - n = 5
2m + 3n = 15
Multiply both sides of the bottom equation by 2 to get:
m - n = 5
4m + 6n = 30
Add the two equations to get: 5m + 5n = 35
Divide both sides of the equation by 5 to get: m + n = 7
Answer: C