Answer:∠?=40°Step-by-step explanation:Remember that in a line AND a triangle there are 180 degrees.You correctly found the third angle in the left triangle to be 69°, Now plug it into the equation for a line, including 71°:69°+71°+x=180°1) Combine the degrees:140°+x=180°2) Subtract 140° from both sides:x=40°We have now found the bottom left angle for the triangle on the right to be 40°To find the angle labeled "?" You must plug in all of the known angles of the triangle to be equal to 180°:40°+100°+x=180°1) Combine the degrees:140°+x=180°2) Subtract 140 from both sides:∠?=40°