Susan mailed y letters in January. She mailed 3 times as many letters in February. In march she mailed 10 letters more than half of what she mailed in January February together. If a letter cost $0.37 to mail, how much money did she spend mailing letters in march?

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.