Solving system of equations by substitution

Question

Solve the system of equations by the substitution method.

 

y=2x+9

y=5x+10

Answer 1

subtract equation 1 from 2

y-y=(2x-5x)+(9-10)

0=-3x-1

add 3x to both sides

3x=-1

divide both sides by 3

x=-1/3

substitute in equation 1

y=2(-1/3)+9=-2/3+27/3=25/3

 

the solution is x=-1/3 and y=25/3