These are made more difficult because you are supposed to figure out what question is being asked in each case.
4. Apparently, you're supposed to determine the fee for rental of each pair of skates. If that fee is represented by x, then the total rental cost for 7 pairs will be 7x. Adding that to the group rate gives the total charge:
... 7x + 9 = 30
5. Apparenly, you're supposed to determine the fraction of a pan of brownies that each student will get. Let that be represented by x. Then the total amount of brownies the 30 students get is 30x. Added to the 7 pans that are donated, the total is the number of pans that were baked.
... 30x + 7 = 9
