S=2(a*b+a*c+b*c)
а=2/15, b=3/4, с=5/12
S= 2(2/15*3/4+2/15*5/12+3/4*5/12)=2(2*3/15*4+2*5/15*12+3*5*4*12)=
=2(1/10+1/18+5/16)=2/10+2/18+10/16=1/5+1/9+5/8=(72+40+45)/360=157/360=0,436
S=2(a*b+a*c+b*c)
а=2/15, b=3/4, с=5/12
S= 2(2/15*3/4+2/15*5/12+3/4*5/12)=2(2*3/15*4+2*5/15*12+3*5*4*12)=
=2(1/10+1/18+5/16)=2/10+2/18+10/16=1/5+1/9+5/8=(72+40+45)/360=157/360=0,436