Question 1056090
x child tickets
y adult tickets
z senior tickets


{{{system(x+y+z=992,11x+14y+8z=11680,(x+y)-2z=287)}}}


You might want to try to first eliminate z, simplify the system to linear equations in x and y; and continue onward to finish.  Alternatively, you could use other standard matrix row reductions or choose substitution method.