John's age is 4 more than 3 time mike's age. if their sum is 20, how old are mike and john?

Let me help you with this :)

John = x 
Mike = y

x = 4 + 3y (4 more than 3 times)

x + y = 20 (we put the x above into this equation)

4 + 3y + y = 20 
4y = 16 (we transfers the 4 on the left side to the right side and subtract it from the 20)
y = 4 (the answer is 4)

we use this for the equation:

x = 4 +3*4
x = 16

John is 16 years old and Mike is 4 years old :)

Rounding decimals is very similar to rounding other numbers. if the hundredths and thousandths places of a decimal is forty-nine or less, they are dropped and the tenths place does not change. for example, rounding 0.843 to the nearest tenth would give 0.8. , your welcome !