21 is 30% of what number?

Let x be the number.

30%x = 21
x = 21/(30%)
x = 21/(30/100)
x = 21/(3/10)
x = 21(10/3)
x = 70

30 Of 21

30%<-------------->21
10%<--------------> 7

100%<------------> 70

consider this
x is y percent of z
or
x = (y/100)(z)
now, substitute
21 = 0.3z
divide both sides you'll get
z = 70

30% = 3/10

30% -> 21
3/10 -> 21
1/10 -> 21/3=7
10/10 ->7x10=70
100%->70

therefore 21 is 30% of 70

70

21 IS 30% OF 70.
21/30 MUNTIPLY 100 =70

If 21 is 30% of this certain number, then it means 7 is 10% of this number.
If 10% is 7, obviously, 70 is the number. :)
Hope this helps.

70

let n = number

convert 30% into decimal: 30% --> 0.3

21 = 0.3n
70 = n --> final answer