"what number" can be expressed as x, because we don't know what it is.
45 is 30% of x
45 = 30% of x
45 = 0.3 of x.
45 = 0.3*x ---Divide both sides by 0.3
45 ÷ 0.3 = x
45 ÷ 3/10 = x
45 * 10/3 = x
450/3 = x
150 = x
So x = 150
This means 45 is 30% of 150.
