Let f be the fathers age and let s be the sons age
f = 60 s = 30
when f = 45
s = 15 which is only a third if his fathers age
when f = 40
s = 10 which is a quarter of his fathers age
therefore when his father was 4 times his age, the son was 10
Step 1:
Solve one of the equations for either x = or y = .
Step 2:
Substitute the solution from step 1 into the other equation.
Step 3:
Solve this new equation.
Step 4:
Solve for the second variable.
Example 1: Solve the following system by substitution
Substitution Method Example
Solution:
Step 1: Solve one of the equations for either x = or y = . We will solve second equation for y.
solution step 1
Step 2: Substitute the solution from step 1 into the second equation.
solution step 2
Step 3: Solve this new equation.
solution step 3
Step 4: Solve for the second variable
solution step 4
The solution is: (x, y) = (10, -5)
Hope this helps!
