Given:
Rectangle: 320 x 190
triangle: base: 305
I'm assuming that the unit measure is in miles.
I found a map of Nevada and I figured that the length of the rectangle is serving as the height of the triangle.
Area of the rectangle = Length * width
A = 320 mi x 190 mi
A = 60,800 sq. mi.
Area of a triangle = (height * base) / 2
A = (320 mi x 305 mi) / 2
A = 97,600 sq. mi / 2
A = 48,800 sq. mi.
Total Area = 60,800 + 48,800 = 109,600 square miles.