to form the two systems, we have to determine the catagories of the 2 equations : one for money and one for the no of packs
after forming the two equations we simply put the numbers in the same order put above on the calculator ( mode 5:1) and the calaculator will answer it in seconds . 10 small packs and 10 large packs.
To check your answer , substitute the letters with their values and if both equations gave you the same value at the end then your answer is correct!