Question 826115
A man is five times as old as his son. Four years ago he was nine times as old. Find their present ages.
For me I use the letter variable of the first letter of the word it stands for to keep it easily understandable in my head.
m=mans age
s=sons age
Ago means past tense so subtraction is required
{{{m=5s}}}
{{{(m-4)=9(s-4)}}}
Use substitution method
{{{(5s)-4=9(s-4)}}}
Distribute the 9
{{{5s-4=9s-36}}}
Subtract 5s from both sides
{{{-4=4s-36}}}
Add 36 to both sides
{{{32=4s}}}
Divide by 4 
{{{8=s}}}
Put back into first equation
{{{m=5(8)}}}
{{{m=40}}}