Question

Twice a number is decreased by 7, and this quantity is multiplied by 3. the result is 9 less than 10 times the number. What is the number?

Answer 1

(7-2x)3 =9-10x

x= -3

Explanation:

we let the number to be x.

twice a number=2x is decreased by 7 that is to say 7-2x, is multiplied by 3, we have (7-2x)3.

the result is 9 less than 10times the number which is =9-10x.

so bringing all these together we have;

(7-2x)3=9-10x.

what is the number?

solving, we have:

(7-2x)3=9-10x

21-6x=9-10x

21-9= -10x+6x

12= -4x

dividing both sides by -4 we have our number

x= -3.

for proof we can substitute x=-3 into the equation.

21-6(-3) =9-10(-3)

21+18=9+30

39=39