The average of two numbers is 18. When 2 times the first number is added to 5 times the second number, the result is 120. How do I find the two numbers?
1 Answer
Oct 17, 2015
Express as algebraic equations in two variables
x = 20
y = 16
Explanation:
Let the two numbers be
We are given:
(x+y)/2 = 18
2x+5y = 120
Multiply both sides of the first equation by
x + y = 36
Subtract
x = 36 - y
Substitute this expression for
120 = 2x+5y = 2(36 - y) + 5y = 72 - 2y + 5y = 72 + 3y
Subtract
3y = 120 - 72 = 48
Divide both sides by
y = 16
Then substitute that into
x = 36 - 16 = 20