To begin with we need to understand what a percentage is. It is simply a proportional that shows a number as parts of a hundred. So 30% is the same as saying 30/100 which can be simplified by dividing the numerator and denominator by 10 to just 3/10.So now we just need to find 3/10 of 70. This can be done by dividing 70 by 10 (the denominator)which gives us the number 7 (70/10= 7)and multiplying by 3 (the numerator) which gives us 21 (7*3 = 21). So our final answer is 21; make sure to show all your working out.