Answer:
B or 31r-71
Step-by-step explanation:
First, use distributive property to expand the first term.
30r-66-(5-r)
Remove the parenthesis of the third term:
30r-66-5+r
Combine like terms
31r-71
20 square meter lawn..............................10 min
10 square meter lawn...............................5 min
30 square meter lawn in.........................5*3=15 min
For the units positions of all numbers we have:

From this we can conclude that total sum of these three numbers is 14. Number 1 we carry to next step. So we have:

For the tens positions of all numbers we have:

The extra number 1 on left side comes from the carry from last step. Similar to ones position we know that total sum is 11.

Now we insert x and z to find out y:

Now we need to find out the product of these three numbers:
He could make 6 squares, because each square has 4 sides. And 24 divided by 4 is 6. The number fact that i used is 24 divided by 4
Uhm i think its 300 - 30 + 30 so the answer is 300