The answer is 91
h0 J% D6 ?; y" @+ T) L2 Z5 l公仔箱論壇1 row 3x4+1x3=15
/ q3 X% m. s, `' o7 @5.39.217.772 row 4x5+2x4=28
# e. [0 z1 d0 E$ E* N3 row 5x6+3x5=45tvb now,tvbnow,bttvb: @( d( x( z2 u/ g+ @! T7 O+ C O
4 row 6x7+4x6=66& Y7 Z* |6 Z/ ^5 D
5 row 7x8+5x7=91  |