Question

a/20= b/7= c/3 e a-b+c=80 alguém me ajuda por favor ?

Answer 1

$\frac{a}{20} =\frac{b}{7} \\ \\ a= \frac{20b}{7} \\ \\ \frac{c}{3} =\frac{b}{7} \\ \\ c=\frac{3b}{7} \\ \\ b=\frac{7b}{7} \\ \\ a-b+c=80 \\ \\ substituindo: \\ \\ \frac{20b}{7}-\frac{7b}{7} +\frac{3b}{7}=80 \\ \\ \frac{20b-7b+3b}{7}=80 \\ \\ \frac{16b}{7}=80 \\ \\ 16b=80.7 \\ \\ b=\frac{560}{16}=35 \\ \\ a=\frac{20.35}{7}=\frac{700}{7} =100 \\ \\ c=\frac{3.35}{7}=\frac{105}{7} =15 \\ \\ Verificando: \\ \\ a-b+c=80 \\ 100-35+15=80 \\ 65+15=80 \\ 80=80$

Answer 2

a-b+c = a/20-b/7+c/3 =80/16

A/20=80/16  16a=1600 
                        a=1600/16    a = 100

B/7=80/16    16b=560
                        b=560/16      b=35

c/3= 80/16    16c=240
                         c=240/16     c=15

a-b+c = 100-35+15 = 80