Given data:
The amount electrician earned is C=$100.
The cost paid to each hardware is c=$2.50
The given profit is P=$75.
The expression for total profit earned after x fixtures is,
P=C-xc
Substitute the given values.
75=100-2.5x
2.5x=25
x=10
Thus, the numbers of fixtures required to get $75 profit are 10.