Hello! Let's work this problem from left to right to make things a bit easier ;)
6.5+(-2) is the same as 6.5-2, since adding a negative is the same as subtracting a positive. 6.5-2=4.5
Now, we have to add 10.5 to 4.5, which gives us the grand total of 15. I hope this helped! Let me know if you need anything else!
40º
7) In this problem, we can see that both tangent lines to that circle come from the same point O.
So, we can write out the following considering that there is one secant line DO and one tangent line to the circle AO

It would be 130/7+4 because 130 is the total divide it by how many she does and add how many she already has
Given:
Wall 1 & 2 : 26 ft by 9 ft
Wall 3 : 18 ft by 9 ft
Area 1 : 26 ft x 9 ft = 234 ft²
Area 2 : 26 ft x 9 ft = 234 ft²
Area 3 : 18 ft x 9 ft = 162 ft²
Total Area : 234 ft² + 234 ft² + 162 ft² = 630 ft²
1 Gallon = 250 ft²
630 ft² ÷ 250 ft² per gallon = 2.52 gallons