If (13+14+15+16)=r(19+112+115+118), then r =

If (13+14+15+16)=r(19+112+115+118), then r =

A 13
B. 43
C. 3
D. 4
E. 12

I do not understand why the answer is 3. The explanation in the Official Guide is not clear at all.

Thanks for your help!