Question 1118347
That "included in" usage is not often (nor ever) found in academic arithmetic or algebra exercise problems.  Maybe you make an attempt to write the problem description correctly so it may be understood.


Here is an attempt to solve the exercise but it might not be the intended interpretation:


y, the son
x, the mother

{{{system(3y+x=75,2x+y=80)}}}



{{{x+3y=75,2x+y=80}}}


{{{system(2x+6y=150,2x+y=80)}}}


Subtract second equation from first equation:
{{{5y=70}}}

{{{highlight(y=14)}}}
-
{{{x=75-3y}}}
{{{x=75-42}}}
{{{highlight(x=33)}}}