Each month, allison gets a $15 allowance and earns $100 working at the theater. she uses the expression 15x + 100y to keep track of her 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 her allowance? (3 points)