Which air mass would produce cold, dry weather in the winter

replace   c   with   a   and simplify.

a = c , b = a, q = n , 2 , a = c , 900 b= a , 700 , q = n , 600 , 2 = b o t h , b = a , q = n

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