Question 1091149
.
Ants have 6 legs (Wikipedia, https://en.wikipedia.org/wiki/Ant).


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

      and ALL have 6 legs (!)
</pre>

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


<pre>
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 = {{{12/2}}} = 6.


<U>Answer</U>.  6 spiders and 19-6 = 13 ants.


<U>Check</U>.   13*6 + 6*8 = 126.   ! Correct !
</pre>

Solved.