He fourth one: 4,5,6,7,8...if it has those two bars || it means absolute value which basically means if its negative you just change it to a posotive :)
1) 55% is girls, then
100-55=45% is boys.
2) 45%=0.45 or 2) 400 ----100%
3)400*0.45= 180 boys x -----45% x=400*45/100=180 boys
Answer is 180 boys.
Volume of one cubic block = (1/6)^3 = 1/216 cu ins
Volume of the prism = 1/3 * 2/3 * 2/3 = 4/27 cu ins
Number of blocks to fill prism = 4/27 / 1/216 = (216*4) / 27 = 32
