The answer is 105 units²
Step-by-step explanation:
Since the middle is a square, the base of all 4 triangles are equal.
Let x be the height of the triangles.
The height of the triangle can be defined as:
15 = 7 + x + x
15 = 7 + 2x
15 - 7 = 2x
x = 8/2
x = 4
Area = area of square + 4(area of triangle)
= (7 x 7) + 4(1/2(7)(4))
= 49 + 56
= 105 units²