I don't know if u can see it, but there.
X=12
Y=15
Z=20
-2x + y =3
use 5 number and put it in above equation to find y, I will use -2,-1,0,1,2
x y
-2 -1
-1 1
0 3
1 5
2 7
Then draw the graph, find another point in the graph which intersect the slope,
lets say i found (-3,-3)which is on the slope
to prove it, i put (-3,-3) in the equation -2x + y = 3
and i got
3 = 3
Thus it is correct.
Instead, break down the shape into rectangles. Next, calculate the area of both rectangles and add them together. The area of the first rectangle is 72 square centimeters and the area of the second rectangle is 50 square centimeters. Together there are 72 + 50 = 122 square centimeters.
That is how u find a irregular figure..hope this help u