I need to know how to solve this algebra question mr smiths

I need to know how to solve this algebra question. mr. smiths dad is 5 times as old as he was 40 years ago. how old is mr. smiths dad?

Solution

x=Mr. Smith\'s Dad\'s age 40-years-ago.

5x=x+40

Let\'s isolate x...
Let\'s subtract x from both sides...
-x+5x=x+40-x
4x=40
Let\'s divide both sides by 4...
4x/4=40/4
x=10
10+40
Mr. Smith\'s Dad is 50-years-old.