Final answer:
By multiplying the number of packages (78) by the number of crayons per package (100), we find Susan had a total of 7,800 crayons.
Step-by-step explanation:
The question involves multiplication to determine the total number of crayons Susan had. If Susan had 78 packages of crayons and each package contained 100 crayons, we need to multiply the number of packages by the number of crayons in each package to find the total.
The calculation would be:
78 packages × 100 crayons/package = 7,800 crayons
Therefore, the answer is (c) 7,800 crayons.