Problem #1:
x = adults
y = children
x + y = 166
2.10x + 0.75y = 293.25
x = 166 - y
Now we substitute the x value on the second equation:
2.10(166 - y) + 0.75y = 293.25
And we solve for y:
y = 41.
Now we substitute the y value on the first equation:
x = 166 - 41
x = 125
There are 125 adults and 41 children