Prove that if m, d, and k are integers and d > 0, then (m + dk) mod d = m mod
d.

From the rules of modular arithmetic, (A+B)mod C= (A)modC +(B)modC

So,  (m + dk) mod d =  (m) mod d+ (dk) mod d

clearly (dk) mod d = 0, as one of the things (dk) mod d represents, is the remainder of dk, when divided by d, which is clearly 0.

Thus

(m + dk) mod d =  (m) mod d+ (dk) mod d= (m) mod d+ 0=(m) mod d

(m + dk) mod d =(m) mod d

This polygon has 4 sides
180(4-2) = 180(2) = 360 degree
80+90+2x + 3x = 360
170+5x = 360
5x = 190
x= 38
measure of angle t is 2(38)= 76
the answer is c. trust me
hope this !