Let's look at an example:
2.24 x 21.6
Do normal multiplication and get
48384 This is not correct, until we put the decimals in. To know how to do this, count the number of decimal spaces from the factors. In 2.24, there are 2, because .24. In 21.6 there are 1 because of .6. This mean three places, so 48384 becomes
48.384
~theLocoCoco
Simon is 13 years old
Let x be Simon's age
Thus 4 years ago his age was (x - 4) and 2 years from now his age is (x + 2)
Hence 5(x - 4) = 3(x + 2)
distributing both sides gives
5x-20 = 3x + 6
subtract 3x from both sides of the equation
5x - 3x - 20 = 6
2x - 20 = 6
add 20 to both sides
2x = 6 + 20 = 26
divide both sides by 2
x = = 13
Simon is 13 years old