Which expression is equivalent to 13 - (-21) ? Choose 1

(Choice A) 
13 + 21

(Choice B) 
-21 - 13

(Choice C)
-13+21

(Choice D)
-21+13

Which math sentence can be used to determine if the triangle is a right triangle?

Multiply. write your answer in simplest form. 3/8 x 5/7

Answer this two poles, ab and ed, are fixed to the ground with the of ropes ac and ec, as shown: two right triangles abc and edc have a common vertex c. angle abc and edc are right angles. ab is labeled 13 feet, ac is labeled 15 feet, ec is labeled 10 feet, and ed is labeled 4 feet. what is the approximate distance, in feet, between the two poles? 11.14 feet16.65 feet14.35 feet15.59 feet