A boy had a box containing a total of 8 spiders and beetles. He counted 54 legs altogether. Find how many of each were in the box (spiders have 8 legs and beetles have 6 legs).
s+ b = 8
8s+6b = 54
You can solve that system and get the answer. Or you can do it without
algebra this way:
A beetle has 3 pairs of legs, and a spider has 3 pairs plus an extra pair. 54
legs is 27 pairs of legs. All 8 critters have 3 pairs, and that accounts for 24
pair, so the extra 3 pairs belong to the spiders. So there are 3 spiders, and
the other 5 are beetles.
Edwin