Answer:
15
Step-by-step explanation:
18 . ( 14 - 9 ) ÷ [ 12 - ( 19 - 13 ) ]
18 . ( 5 ) ÷ [ 12 - 6 ]
90 ÷ 6
This is a right triangle. If the triangle were laid down, on an end, a right angle would be visible.
D
±1, ±2, ±7, ±14