Serena's mom is planning her birthday party. She bought balloons, plates, and cups. Serena's mom bought twice as many plates as cups. The number of balloons Serena's mom bought was half the number of cups.

a. If Serena's mom bought 84 items, how many of each item did she buy?

b. Tammy brought 12 balloons to the party. How many total balloons were at Serena's birthday party?

c. If half the plates and all but four cups were used during the party, how many plates and cups were used?

a. There were 24 cups, 48 plates, 12 balloons

b. 24 balloons were at the party.

c. 24 plates and 20 cups were used

Step-by-step explanation:

We need to identify first the number of cups so that we can double the quantity for plates and divide the number to get the balloon number.

So if we have 24 cups and we double it we have 48 plates and if we divide in half to get the balloon number we get 12 balloons, which in total is 84.

Then we just need tu add the 12 balloons Tammy brought to have 24 balloons, and at the end to obtain how many plates and cups were used we just need to subtract the items left to the items bought so we get half plates from 48 is 24 plates and 24 cups minus 4 cups left we have 20 cups used in the party.

The important number that we firstly need to calculate is the one that need to be multiply or divided in order to obtain all the results.