Charlies mother would have paid $30 and Charlie would have paid $10.
We get this answer by first converting the percentages into decimals.
75% = 0.75
25% = 0.25
Next we are going to multiple but of the decimals by 40,
0.75 * 40 = 30
0.25 * 40 = 10
And 30 + 10 = 40 so we know we have the right anwser.
= $30 & $10