### Solution:

Here we are given the length of the room as 12 m.The breadth of the room is 10 m and

The height of the room is 7.5 m.

Our room will be in the shape of a cuboid having walls as the shape of a rectangle.

Cuboid looks like this:

We need to find the area of four walls, which means we need to find the area of four rectangles ABCD, EFGH, ADEH and BCFG.

Let us calculate areas of the rectangle. Area of the rectangle having length and breadth is given by A= l×b.

For ABCD, we have length as 12m and height as 7.5 m. So,

Area becomes equal to ⇒(12×7.5)m2 = 90m2.

Similarly for EFGH, we have length as 12m and height as 7.5 m. So,

Area becomes equal to ⇒(12×7.5)m2 = 90m2.

For ADEH, we have breadth as 10m and height as 7.5 m. So,

Area becomes equal to ⇒(10×7.5)m2 = 75 m2.

Similarly for BCFG, we have breadth as 10m and height as 7.5 m. So,

Area becomes equal to ⇒ (10×7.5)m2= 75 m2.

Now the area of all four walls will be equal to the sum of rectangles ABCD, EFGH, ADEH and BCFG. So we get:

Area of four walls ⇒ (90+90+75+75)m2 = 330m2.

Hence the required area of the wall is 330m2.