Question

A spider has 8 legs, a dragonfly has 6 legs. Given a number of spiders and
dragonflies altogether have 420 legs, number of spiders are 3 times the
number of dragonflies, the number of spiders are?

Answer 1

8s+6d=420
3D= s
8s+6(s/3)=420
10s=420
s= 42