First, divide 325 by 4, which will come out to be 81.25, then take the 85 that his mom gave him and subtract the 81.25 to get your answer, which is, 3.75 :)
So to get this, you just divide 28 by 7 because when you are funding a fraction of. number and the numerator of that fraction is 1, you divide the original number by the denominator. 28 ÷ 7 = 4 Hope this helps!