The answer is 91
* {& p) ]& a' z1 o, stvb now,tvbnow,bttvb1 row 3x4+1x3=15公仔箱論壇% w7 |# W% q4 w) i
2 row 4x5+2x4=28
8 i6 w% O ?- ?( M2 X! uos.tvboxnow.com3 row 5x6+3x5=45tvb now,tvbnow,bttvb0 A" J! x" |& g, f2 _2 y
4 row 6x7+4x6=66& |4 k5 H; G2 R2 s: U1 q& E5 d! {
5 row 7x8+5x7=91  |