I like his method better. But here is an alternate way to approach the
problem.
a group of people planned a trip that had a fixed cost of $30,000. later 20
more people wanted to go causing the average cost to decrease by $50 per
person. How many people were planning to go originally?
At first, there were x people each paying $y and that made up the $30,000. To
say that mathematically, we put down what we do in equation form, multiply
people by dollars to get total dollars:
(x)($y) = $30000
or just
xy = 30000
But later, instead of only x people going on the trip, there were now x+20
people going. Then the price per person went down from $y to $(y-50). Again,
to say that mathematically, we put down what we do in equation form, multiply
people by dollars to get total dollars:
(x+20)(y-$50) = $30,000
or just
(x+20)(y-50) = $30,000
So we have the system of equations
Can you solve that system? You'll get two pairs of answers for x and y, one
positive and one negative, and you'll discard the negative answer.
If you have trouble solving it, tell me about it down below.
Edwsin