Question

A fourth grade class has 20 students. The number of girls is 7 less than twice the number of boys. How many boys are in the class?

Answer 1

Answer: There are 9 boys.

Step-by-step explanation

To solve this problem, we have to build a system of two equations, using b to represent the boys and g to represent the girls, we can translate the sentence into an algebraic expression.

• Equation 1: ",A fourth-grade class has 20 students":

`b+g=20`

• Equation 2: ",The number of girls is 7 less than twice the number of boys.":

`g=2b-7`

To solve, we can replace the expression for g (Equation 2), into the Equation 1 and solve for b:

`b+(2b-7)=20`
`b+2b-7=20`
`3b-7=20`
`3b=20+7`
`3b=27`
`b=(27)/(3)`
`b=9`

Thus, there are 9 boys.