(25a + 9d) - (10a - 5d)

Me. i can't figure out this question. give an explanation too. .

X^2/100+y^2/25=1 the length of the major axis is: a)5 b)10 c)20

Ashley spent half of her lunch money on a turkey sandwich. then she spent two-thirds of the money she had left on a bottle of juice and the rest of the money on a cookie. if the cookie cost $.75, how much lunch money did ashley have to start with?