Prove that if a1b1c1 and a2b2c2, then a1+a2b1+b2c1+c2.

Lesson Parent: 
Problem: 

Prove that if a1b1c1 and a2b2c2, then a1+a2b1+b2c1+c2.

Answer: 

It is true that if a1b1c1 and a2b2c2, then a1+a2b1+b2c1+c2.