Question

Solve the system of equations using the substitution method.
4x + 5y = 7
y= 3x + 9
​

Answer 1

x = -2

y = 3

Explanation:

Since y = 3x +9, substitute this value in the first eq.

4x + 5(3x+9) = 7 ===> 4x + 15x + 45 = 7 ===> 19x = 7-45 ==> 19x = -38 ===>

===> x -38/19 ===> x = -2

Replace this value in the second eq.

y = 3(-2) + 9 ===> y = -6 + 9 ===> y = 3