1. The number they aren't given us can be represented by x.
2x (twice the sum of a number)+9 (and 9)=(is equal to) 3* (three times) (x-4 (the difference of the number and four))
2x+9=3*(x-4)
2x+9=3x-12
9=x-12
x=21
2. He is already spending 28.95 for each day, since he is renting for four days, multiply that by four. So far he has already spent $115.80. He has (150-115.80=34.20) $34.20 left. .28 per mile is charged, and since he has 34.20 left he can only use as many times as 28 goes into 34.20. 34.20/28=your answer
