Question

Your math teacher announces a 50 point quiz tomorrow. There will be a total of 15 questions. Some of the questions will be worth 4 points and some of the questions will be worth 3 points. Use a system to find out how many 4 points questions there will be

Answer 1

3x + 4y = 50

x + y = 15

Five 4-point questions

Explanation:

Change x + y = 15 to determine what y equal

y = (-x) + 15

Plug it in the original equation using the substitution method

3x + 4(-x + 15) = 50

3x - 4x + 60 = 50

Combine like terms:

-x = -10, two negative signs equals a positive. x = 10

Plug 10 in for x in the equation x + y = 15

10 + y = 15

Subtract 10 from both sides

y = 5