Each month, matthew gets a $25 allowance and earns $100 mowing lawns. he uses the expression 25x + 100y to keep track of his earnings. part a: identify the variables and coefficients in the expression. (3 points) part b: how many terms are in the expression, what are they, and how do you know? (4 points) part c: which term in the expression shows the total earned from mowing lawns? (3 points)