To answer this question you need to create 2 equations:
S+C=50
2.50S+3.75C=3.35*(50)
S=50-C -so now you can plug in S into the second equation
2.50*(50-C)+3.75C=167.5
Now you just need to solve this equation, the final answer will be 34 pounds of colombian coffee and 16 pounds of sumatra coffee
If we want to has 100 in the denominator we have to divide numerator and denominator by 2. Then total value of fraction doesnt change.

Now read the fraction, its 23 hundreds, now just write as decimal, so,
0.23