Please help and explain!!!!

Answer:
The expression is: 100 -a - 2b
Step-by-step explanation:
One piece of length a and two pieces of length b, i.e., (2 times b) are a total length of (a + 2b). We are asked to express the remaining part of the wire, originally 100 cm long, so that must be 100 minus the total pieces cut out:
100 - ( a + 2b ) = 100 -a -2b