vì\(\dfrac{a}{2}\)=\(\dfrac{b}{4}\)=\(\dfrac{c}{5}\)=>\(\dfrac{5a}{10}\)=\(\dfrac{b}{4}\)=\(\dfrac{3c}{15}\)

áp dụng tính chất của dãy tỉ số bằng nhau ta có:

\(\dfrac{5a}{10}\)=\(\dfrac{b}{4}\)=\(\dfrac{3c}{15}\)=\(\dfrac{5a-b+3c}{10-4+15}\)=\(\dfrac{42}{21}\)=2

vì\(\dfrac{5a}{10}\)=2=>5a=2*10=20=>a=20:5=4

\(\dfrac{b}{4}\)=2=>b=2*4=8

\(\dfrac{3c}{15}\)=2=>3c=2*15=30=>c=30:3=10

vậy a=4,b=8,c=10

ko nhìn dc bạn ơi