Question

daca c×(3+d)=140si c×d=125, calculeaza pe c

Answer 1

$c\cdot(3+d)=140\\c\cdot d=125\leftrightarrow d=\frac{125}{c}\\ c\cdot(3+d)=140\leftrightarrow 3c+c\cdot d=140\leftrightarrow 3c+125=140\leftrightarrow3c=140-125\\\leftrightarrow3c=15\leftrightarrow c=15:3=5\\d=\frac{125}{5}=25$