Write a system of equations to describe the situation below, solve using substitution, and fill in the blanks
William is collecting pledges for a walk-a-thon. His mother has pledged a flat donation of $21,
and his grandmother has pledged $1 per kilometer. If William walks a certain distance, the
two donors will end up owing the same amount. What is that distance? How much will each
donor owe?
If William walks
kilometers, his mother and grandmother will eac