Answer:
The amount of minutes Grace has to use her cell phone this month is 59 minutes
Step-by-step explanation:
Let
x -----> amount of minutes Grace has to use her cell phone this month
we know that
The average usage during the four months is equal to the sum of the minutes used in the four months divided by four (the number of months)
so
[tex]55=\frac{42+62+57+x}{4}[/tex]
Solve for x
Multiply by 4 both sides to remove the fraction
[tex]55(4)=(42+62+57+x)[/tex]
[tex]220=(161+x)[/tex]
[tex]x=220-161[/tex]
[tex]x=59\ min[/tex]
therefore
The amount of minutes Grace has to use her cell phone this month is 59 minutes