Arecipe calls for 2 2/4 cups of raisins but julie has only a 1/4 cup. how many 1/4 cups does she need to measure out?

a_n = a_1 + (n - 1)d

the first term is 6.

the common difference d = ?

when you find d, replace n with 7 and d with the common difference to find your answer.

multiplication is multiplication.   it might feel harder depending on what level of math you are in, but generally it will be the same old stuff, while implementing some new concepts and methods of solving work.