Name: Hank

Question: I have been unable to determine what formula to use to solve this problem:

what number doubled plus 20 will give you 4/3 the original number

2 x__ + 20 = 4/3 of the original number

thank you

Hi Hank,

your line

2 x__ + 20 = 4/3 of the original number
shows the need for some algebra. On the left side of the equation you have "___" to indicate the original number and on the right side you have the phrase "the original number". The algebraic method is to use some symbol, usually a letter, to designate the unknown number. Suppose that N is the original number then you question becomes "Find N if 2 x N + 20 = 4/3(N)".

The first thing I would do with this equation is to multiply both sides by 3 to eliminate the fraction.

2 x N + 20 = 4/3(N)

6 x N + 60 = 4 x N
Now subtract 4 x N rom both sides

6 x N + 60 - 4 x N = 4 x N - 4 x N

2 x N + 60 = 0

Adding -60 to both sides gives 2 x N + 60 - 60 = - 60

2 x N = - 60 and hence N = - 30.

Cheers,
Penny
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