Julio bought a total of 20 medium and large pumpkins. if he spent $53 and bought 6 more large pumpkins as medium pumpkins, how many large pumpkins did he buy?

20 medium and large pumpkins

m ... number of medium pumpkins
l ... number of large pumpkins

20 = m + l
20 = m + (m + 6)
20 = 2 * m + 6
2 * m = 20 - 6
2 * m = 14
m = 7 medium pumpkins

l = 20 - 7 = 13 large pumpkins

Result: Julio bought 13 large pumpkins.