SOLUTION: Lisa keeps ants and spiders as pets. She counted the legs and heads of these pets and found that there were 126 legs and 19 heads. How many ants were there?

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Question 1091149: Lisa keeps ants and spiders as pets. She counted the legs and heads of these pets and found that there were 126 legs and 19 heads. How many ants were there?
Answer by ikleyn(52884) About Me  (Show Source):
You can put this solution on YOUR website!
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Ants have 6 legs (Wikipedia, https://en.wikipedia.org/wiki/Ant). 

      It is amaizing: there are 22000 estimated species, of them 15000 classified,  

      and ALL have 6 legs (!)

Spiders have 8 legs (Wikipedia, https://en.wikipedia.org/wiki/Spider). 

Equations:

 A +  S =  19,       (1)   heads,   and
6A + 8S = 126        (2)   legs.


Multiply (1) by 6 (both sides). You will get

6A + 6S = 114,       (1')
6A + 8S = 126.


Now subtract (1') from (2') (both sides). You will get

2S = 126 - 114 = 12  ====>  S = 12%2F2 = 6.


Answer.  6 spiders and 19-6 = 13 ants.


Check.   13*6 + 6*8 = 126.   ! Correct !

Solved.