they have the same angles.
in order for two triangles where you know the side lengths to be congruent, their sides must be in the same ratio at all times. if this s not satisfied, they are not similar. this means that kj / rs = kl / ts = jl / rt, or 15 / 12 = 20 / 16 = 25 / 20, or 5/4 = 5/4 = 5/4. this means that the two triangles are similar.
finally, this implies that they have the same angles.
∠a = 40°
∠c = 32°
inscribed angles that intercept the same arc have the same measure.
∠a intercepts the same arc (cd) as ∠b, so has the same measure, 40°.
∠c intercepts the same arc (ab) as ∠d, so has the same measure, 32°.
answer: 15 1/2
step-by-step explanation: you have to divided 31 by 2=15.5=15 1/2