Answer:
The number of locks will be 3
The total cost = $50
Step-by-step explanation:
We are trying to write the equations of the cost in the form of the equation of a straight line
The equation will be;
C = F + 15r
where F is the price for house lock , C is total cost and r is the amount per rekey
For the first locksmith;
His equation will be ;
C = 25 + 15r
For the second
C = 10 + 20r
If the total cost is the same for both;
then;
10 + 20r = 25 + 15r
20r - 15r = 25 - 10
5r = 15
r = 15/5 = 3
For the total cost to be same, number of locks is 3
The total cost will be ;
C = 20 + 10(3) = 20 + 30 = $50