You can put this solution on YOUR website!
The linear equation for calculating cost based on hours of labor,
C(x)=49x+21 has a slope of m=49 and a C-intercept of b=21.
The slope, m=49 is the hourly rate. (Each additional hour of labor increases the cost by $49).
The intercept, b=21, is the base cost for the service call. If you called and made the repairman go to your house, you have to pay $21 for the call, even if you had figured it out and fixed the computer yourself just before the repairman rang your doorbell. The time and expense of traveling to your house has to be paid for.