When hydrogen is used in a fuel cell, the only waste product is/are

A) nitrogen oxides
B) carbon dioxide
C) methane
D) water
E) none of the above

D) water

Explanation: When pure hydrogen is used as the fuel, the only by-products generated from the fuel cell are pure water and heat.

if triangle abc is congruent to triangle def, their interior angles are congruent, because congruent parts of congruent triangles are congruent (cpctc).

that means ∠d is congruent to ∠a; ∠d is equal to 8x - 2.

interior angles of all triangles add to equal 180 degrees, so you can set the sum of these interior angle values equal to 180 and solve for x.

180 = (8x - 2) + 22 + 72

180 = 8x - 2 + 22 + 72

180 = 8x + 92

88 = 8x

11 = x

x = 11