Question

The sum of two numbers is 40. The second number is 5 less than twice the first number. Let x represent the first number and let y represent the second number. What is the value of the first number? Use the table to guess and check. 15 20 25 30

Answer 1

Explanation:

X+2x-5= 40

3x-5=40

+5=+5

3x=45

3x/3=45/3

X=15

Answer 2

The value of the first number is 15

Explanation:

The sum of two number is 40 would be:

`x+y=40`

The second number is 5 less than twice the first number would be:

`y=2x-5`

Now, we can find the value by solving this system of equations, we will isolate x in the first equation, then we replace it in the second equation:

`x=40-y`

`y=2(40-y)-5\\y=80-2y-5\\y+2y=75\\3y=75\\y=(75)/(3)=25`

Then, we replace this value in one equation of find the other variable:

`x+25=40\\x=40-25\\x=15`

Therefore, the value of the first number is 15 and the second number is 25.