First, we want to turn the words into math equations. For equation (1), let's set it equal to Roberto's piggy bank (y)
y=5x+30
He starts off with $30 and adds 5 every week, or 5x where x is in weeks.
The second equation for Jack this time, is he has 0 starting cash, and adds $8 every week or 8x, so his equation is
y=8x+0
Next, set these two equations equal to each other to find out how many weeks (x) the boys will have to wait to have the exact same amount of money.
5x+30=8x
Subtract 5x from both sides to keep it equal.
30=3x
Divide by 3 on both sides
10=x
And you have your answer! After 10 weeks, they will both have the same amount of money.
