Answer:
Grant can purchase 7 base ball cards packs in $21.
Step-by-step explanation:
Grant paid $12 for 4 baseball card packs.
So, in $1 he will purchase, [tex]\frac{4}{12}[/tex] cards
And in $21, he will purchase [tex]\frac{4}{12}\times21[/tex] = 7
Therefore, Grant can purchase 7 base ball cards packs in $21.