Question

Adriel is x years old and her younger sister is y years old. The sum of thei ages is 7. The difference of 3 times adriels age and her sisters age is 9. The related sum of the linear equation is x+y=7 3x-y=9. Solve the linear equations. Then find adriels age and her sisters age

Answer 1

set one of the equations to equal x or y

(substitution method)

x=7-y plug this into the other equation

3(7-y)-y=9 distribute

21-3y-y=9 --> 21-4y=9

get y alone

-4y=9-21--> -4y=-12 divide by -4 to solve

y=3 sisters age

plug this in to one of the equations to get Adriel's age

x+3=7

x=7-3

x=4 Adriel's age