Write a system of equations to describe the situation below, solve using any method, and fill in the blanks.
An employee at a party store is assembling balloon bouquets. For a graduation party, he assembled 6 small balloon bouquets and 3 large balloon bouquets, which used a total of 144 balloons. Then, for a Father's Day celebration, he used 84 balloons to assemble 1 small balloon bouquet and 3 large balloon bouquets. How many balloons are in each bouquet?
The small balloon bouquet uses ___ balloons and the large one uses ____ balloons.
