Tentukan hasil aljabar

A.13a-8b+21a+9b
=13a+12a-8b+9b
=25a+b
B.15i-14j+13k-30i-45j+51k
=15i-30i-14j-45j+13k+51k
= -15i -59j+64k
C.3x-17y+35z+4x+23y-92
=3x+4x-17y+23y+35z-92
=7x+6y+35z-92