tentukan hasil perjumlahan bentuk aljabar berikut:a.(13a-8b)+(21a+9b),b.(15i-14j+13k)+(-30i-45j+51k),c.(3x-17y+35z)+(4x+23y-9z)

a. (13a-8b) + (21a+9b) = (13a+21a)+(-8b+9b)
= 34a+b
b. (15i-14j+13k) + (-30i-45j+51k) = (15i-30i) - (14j-45j) + (13k+51k) = -15i + 31j + 64k
c. (3x-17y+35z) + (4x+23y-9z) = (3x+4x) - (17y+23y) + (35z-9z) = 7x-40y+26z