Let j = Jason's age
Let z = Zack's age
j = 11z // Jason is 11 times older than zack
j + z = 48 // The sum of their ages in 48
j = 11z becomes j - 11z = 0
j - 11z = 0
j + z = 48
Multiply the top equation by -1
-1(j - 11z) = (0)-1
-j + 11z = 0
-j + 11z = 0
j + z = 48
Add both equations to cancel the j terms.
12z = 48
Divide both sides by 12.
z = 4
Zack is 4 years old and Jason is 44 years old.
