2) Fish can't fly in the sky.

Doctors often help patients in hospitals.

Mike had a good time. He is very (happy).

5) Look at the traffic lights. It is (green). Let's go.

3X+2Y+Z=392①

X+3Y+2Z=400②

2X+Y+3Z=336③

Solution: from ②×3: 3X+9Y+6Z= 1200④.

From ④-①: 7Y+5Z=808⑤.

From ②+③: 3X+4Y+5Z=736⑥.

From ⑥-①: 2Y+4Z=344⑦。

Recombine ⑤ and ⑤ into an equation: 7Y+5Z=808⑤.

2Y+4Z=344⑦

Solution: Y=84

Z=44

Substitute Y=84 and Z=44 into ① to get X=60.

The solution of the original equations is: X=60.

Y=84

Z=44