1. Students plant trees, and senior students plant trees 180, which is twice as much as middle school students, and middle school students plant trees three times less than junior students? How many trees are planted in the lower grades?

Medium grade: (180-4)÷2=88 trees.

Lower grades: (88+? )÷3

2. Dad 40 yuan bought 7 plates and 4 bowls, and Mom 32 yuan bought the same 5 plates and 4 bowls. How much is each plate? How much is each bowl?

Each set: (40-32)÷(7-5)=4 yuan.

Each bowl (40-4×7)÷4=3 yuan.

3. He Ding * * has 240 stamps. If Ding Xiao gave Xiao Pang 50 stamps, Xiao Pang now has exactly three times as many stamps as Ding Xiao. How many stamps did Xiao Pang and Ding Xiao originally have?

Little Dingding: (240+50× 2) ÷ (1+3) =110.

Xiao pang: 240-110 =130.