16)x=2y/3; z=7y/4
x+y+z=82
2y/3+7y/4+y=82
12y+8y+21y=82
41y=82
y=2
x=2*2/3=4/3
z=7*2/4=7/2
x*y*z=4/3*2*7/2=28/3=
17)n(n+1)=132
2n;2(n+1)
nok 2n(n+1)=2*132=264
18)
skorost lodki 60km/ch
skorost techenie reki x
o techenie 60+x 7(60+x)
protiv techenie 60-x 8(60-x)
polucitsya 8(60-x)-30=7(60+x)
480-8x-30=420+7x
30=15x
x=30:15
x=2 km/ch
skorost vodi 2km/ch