To find out how much Jason earned babysitting, we first need to determine the total amount of money he earned.
Let's start by figuring out the total cost of the skateboard and helmet. The skateboard costs $45.50 with tax, and the helmet costs $18.25 with tax. So, the total cost of both items is 45.50 + 18.25 = $63.75.
Next, we know that Jason earned 1/3 of the total amount by mowing lawns. To find out how much this is, we need to divide the total amount by 3: 63.75 / 3 = $21.25.
Now we can calculate how much Jason earned babysitting. Since the amount he earned from mowing lawns is $21.25, the remaining amount must be what he earned from babysitting. Subtracting $21.25 from the total amount, we get: 63.75 - 21.25 = $42.50.
Therefore, Jason earned $42.50 from babysitting.