If
\(\begin{cases} a+b=17 \\ c+d=20 \\ a-d = \frac{d-c}2 = 1 \end{cases}\)
find (b + c)/(a - b).
+357 First off, we substitude a=17-b
c+d=20
17-b-d=1
17-b-d=(d-c)/2
Then we substitude c=20-d
17-b-d=1
17-b-d=(d-[20-d])/2
Substitude
17-(-d+16)-d=(d-[20-d])/2
Which, when simplified and drawn out gives us d=11
Substitude b=-d+16
B=5
Plug it into C=20-d
c=20-11
c=9
Add it to a=17-b
a=17-5
a=12
So we get to our last equation:(5+9)/(12-5)
14/7
14/7=2
Yay!
