What the answer for 0+4t=7t+15

Find the missing part. use an improper fraction for your answer.

Cindy uses 1-inch cubes to find the volume of a jewelry box shaped like a rectangular prism. she uses 780 cubes to completely fill the jewelry box with no gaps or overlaps. if the jewelry box is 13 inches long and 5 inches wide, how tall is cindy’s jewelry box?

Free 100 points to whoever says “oof the porridges” if it’s not exact, your answer will be reported, first person gets brainliest