3 7/8 Converted into decimal equals 3.875
7/8 = 0.875 + 3
So 45% OF 40 is
45% * 40
0.45 * 40
that is 18
18 is 18% of what number?
18 = 18% * x
18 = 0.18 * x
divide both sides by 0.18
100 = x
45 % of 40, which is 18, and is 18% of 100.
Hope this helps
