Answer:
She used 87 minutes last month
Step-by-step explanation:
Step 1: Express the total monthly phone bill
The total monthly phone bill can be expressed as follows;
A=F+(R×M)
where;
A=total monthly phone bill
F=fixed income per month
R=additional rate per minute
M=total number of minutes
In our case;
A=$123.75
F=$102 per month
R=$0.25 per minute
M=m
replacing;
123.75=102+(0.25 of m)
123.75=102+(0.25×m)
123.75=102+0.25 m
123.75-102=0.25 m
0.25 m=21.75
m=21.75/0.25
m=87 minutes
She used 87 minutes last month
