`(20+25xx45)xx15(12-4)`

To compute this, follow the order of operation known as PEMDAS.

So, simplify the expression inside each parenthesis.

For the first parenthesis, since there are two operations inside it, apply order of operation too. So, multiply the two numbers 25 and 45.

`20+25xx45`

`=20+1125`

Then, add.

`=1145`

Hence, the expression inside the first parenthesis simplifies to:

`20+25xx45= 1145`

For the second parenthesis, since there is only one operation inside it, proceed to subtract the two numbers.

Hence, `12-4=8` .

Now that the expression inside each parenthesis are simplified, the whole expression becomes:

`(20+25xx45)xx15(12-4)`

`= 1145 xx15xx8`

Since only one operations remains, multiply the three numbers.

`=137400`

**Therefore, `(20+25xx45)xx15(12-4)=137400` .**