The sum of two times a number and five is eight

Question

The sum of two times a number and five is eight

Answer 1

Since the number is unknown, we'll call it x. So if 2 times the number (x) plus 5 equals eight, you would write this as the equation 2x + 5 = 8. In order to solve for x, you need to get rid of the 5 and the coefficient (the number in front of the x). First, get rid of the 5 by subtracting 5 from both sides of the equation (to make sure the equation stays correct, you need to do the same thing to both sides), so

2x + 5 - 5 = 8 - 5.

2x = 3.

Now, to get rid of the 2, divide each side of the equation by 2:

2x/2 = 3/2

x = 3/2 (or 1 1/2 or 1.5)

To check your answer, substitute 3/2 (or 1.5) for x in your original equation like so:

2x + 5 = 8

2(3/2) + 5 = 8

6/2 + 5 = 8 (to multply a whole number by a fraction, you write the whole number as a fraction (2/1, then multply the numerators and denominators)

6/2 = 3, so

3 + 5 = 8. Since this is a true statement, you know you got the right answer. :-)