Question 974375
He starts with Y toy cars. Y is an unknown number of cars that we'll have to find out.
.
Start : Y
.
He gives away 11.
.
Y - 11
.
His dad gives him twice as many as he had in the beginning. In other words, he gives him twice the amount of what he started with. He started with Y, so his dad gives him 2*y. We add this 2Y on top of the Y - 11 he currently has :
.
Y - 11 + 2Y
.
Finally, we're told this final amount adds up to 55 toys.
.
Y - 11 + 2Y = 55.
.
That's our equation, we need to solve it to find Y :
.
Y - 11 + 2Y = 55
.
We group the Y and 2Y together :

3Y - 11 = 55
.
We add +11 on both sides:

3Y = 55 +11
.
3Y = 66
.
Y = 22

So the original amount of toys was 22.
.
Hope that helps!