Question 36545
(.8*20+.7*30)/50=(16+21)/50 or 37/50=.74 grade for all 50 students.

100+9=109 the number opposite #9 100 is opposite 0 then add 9 to each we get 9 & 109

m+m/2+3m=99 or 4m+m/2=99 or (8m+m)/2=99 or 9m/2=99 or 9m=99*2 or 9m=198 or m=22

thus Mary is 22 Toms 1/2*22=11 & Sally is 3*22=66 thus 22+11+66=99 or 99=99 

a 9*12*5 cube has 2 faces 9*12=216 now we have 2 faces 3*9=54 & 2 faces 3*12=72
adding up all these exclusive faces we get 216+54+72=342