Answer:
Draw all the three triangles and label them.
First triangle perimeter is 20 + c + a
The second is (20+15) + 70 + (30+a)
Third is (20+35+12) + d + (a+30+b)
Now we need to find scale factor (s.f) from on triangle to the other.
35/20 = 1.75 s.f.
Thus, 70/1.75 = c and it's 40
Now use pythag to find a
A = square root of 20^2 + 40^2
=44.72
(a+30) = 74.72
47/35 = 1.34 s.f.
70/1.34 = d and it's 52.13
Now pythag again to find b
A = square root of 47^2 + 52.13^2
^2 = 70.19
So, a+30+ b = 70.19
40+30 + b = 70.19
b= 70-70.19
b= 0.19
A=40
B=0.19
C=40
D=52.13
Hope this helps!