Answer:
Train A = 214
Train B = 86
Step-by-step explanation:
a + b = 300
a - b = 128
a = 128 + b
(128 + b) + b = 300
128 + b + b = 300
128 + 2b = 300
2b = 300 - 128
2b = 172
b = 172 ÷ 2
b = 86
a = 128 + (86)
a = 214
Answer: -4m-n
5m-13m-n+4m
5m-13m+4m-n
-8m+4m-n
-4m-n