You do the sum(40) subtracted by 8, the answer from that divided by 2 since Erin's two times younger.
40-8=32
32÷2=16
Then if you want to check it you do the opposite and get the same sum(40) so 16×2=32 and 32+8=40
The given system of equation that is
and
has infinite number of solutions.
Option -C.
<u>Solution:</u>
Need to determine number of solution given system of equation has.

Let us first bring the equation in standard form for comparison


To check how many solutions are there for system of equations
, we need to compare ratios of 
In our case,



As
, so given system of equations have infinite number of solutions.
Hence, we can conclude that system has infinite number of solutions.
Really any option.
Explanation: A triangle can be obtuse of acute, either of these answers will make one of those.