Two​ trains, Train A and Train​ B, weigh a total of 215 tons. Train A is heavier than Train B. The difference of their weights is 127 tons. What is the weight of each​ train?

Answer 1

A + B = 215 (the trains weigh a TOTAL of 215 TONS)

A - B = 127 (if you subtract the weight of the lighter train from that of the heavier, you get the difference)

Looks like addition/ elimination technique works quite easily here because the variable B has opposite numerical coefficients in the two equations (equals added to equals are equal).

2A + 0B = 342 (normally would not show the 0B, just displayed for emphasis)

2A = 342

A = 171 (342/2 = 171)

To find B:

171 + B = 215

B = 215 - 171 = 44 Tons

Check the difference:

171 - 44 = 127 (check)