First, it seems that primary schools can't solve the ternary linear equations. Analyze by ratio and proportion:

1 of willow equals 1 of poplar, that is, willow: poplar = 3: 4? Namely: willow = 3/4 poplar.

Poplar 1 is as much as locust 1. That is, poplar: locust tree = 5: 2, that is, locust tree = 2/5 poplar.

Next, you can list the equation solutions:

Set X poplar and 3/4 willow? X tree, Sophora japonica 2/5? X tree

( 1+3/4+2/5)x=860，

X = 400 ... Poplar

3/4x = 300 ... Willow.

2/5x = 160 ... Sophora japonica

Second,

Analysis: Because? Not planted: planted = 3: 5, that is, the number of trees not planted = 3/5 of the number of trees planted.

Assuming that the total number of plants is X, 0. 15x plants were planted on the first day, and 3/5 plants were seedless (0. 15x+ 190).

Column equation: (1+3/5) × (0.15x+190) = X.

Solution: x = 400 (tree)