Explicație pas cu pas:
a:b=3=>a=3b
b:2=c=>b=2c
dacă a=3b si b=2c=> a=3×2c=6c
a-b=40=> 6c-2c=40=> 4c=40=>c=40:4=10
=>b:2=10=>b=10×2=20
=>a-20=40=>a=40+20=60
=>3a-4b+5c=3×60-4×20+5×10=180-80+50
=100+50=150
