The bottom shape can be multiplied just like a normal rectangle because the part cut off without measurements fits into the part with measurements. area is length x width so
23 x 38 = 874cm squares.
The top is the same so
48 x 70 = 3360 like you already had.
The total shape’s area is the two shapes added together which is
874 + 3360 = 4234
The final answer is 4234cm squared