The intersecting secant-tangent theorem says that

where T is the point at which line segment PO touches the circle. Similarly,

so we have

OP is of course as long as itself, and AO and BO are radii of the same circle so they have the same lengths.
This means triangles APO and BPO are congruent, which means angles APO and BPO are congruent, so angle APB is bisected by PO.
You just divided 1/2 (.5) by 10 which is .05. so the answer is 0.05 gallons
Answer:
A parallelogram has 180 degrees of rotational symmetry
Have you learned PEMDAS? (Parenthesis, exponents, multiplication, division, addition, subtraction). That is what I am going to do here.
The first parenthesis, let's solve. 7*10=70-5=65
The second parentheisis: I am assuming the negative sign is a typo, and this answer will be off if it is not. Sorry. 5*10=50
65*50=3250
I hope this helps, and let me know if you need further assistance.