Ans given below
42-6=-2d
36=-2d
d=-18
the answer is three digits because the answer is 157.136
X= number of adult tickets sold
y= number of kids tickets sold
7x+20y=236
21x+50y=618
solve for x
keeping in mind that perpendicular lines have negative reciprocal slopes, let's check for the slope of the equation above

therefore then


Substitute the value of x = 2 to the equation:
