Sorry, why didn't I answer this sooner?
Answer:
114 units^2
Step-by-step explanation:
I know I know it's a bit weird and childish answer, but it works, really, all you have to do given the dotted line is:
2*12=24
15*12=180
180/2, since it's not a rectangle, but half of it, think of it like a rectangular sandwich. Cut it in half diagonally and it's still half.
180/2=90
90+24=
<u>114</u>