tolong dong kk abang jawabkan nomor 7 please pake cara yaa

a = 3(i) -2(j)
b = -(i) + 4(j)
r = 7(i) -8(j)
r = ka + mb

ka = 3k(i) -2k(j)
mb = -m(i) + 4m(j)

r = ka + mb
7(i) -8(j) = [3k(i) -2k(j)] + [-m(i) + 4m(j)]
(kita gabungkan, i dengan i, j dengan j
7(i) -8(j) = [3k -m](i) + [-2k + 4m](j)

7 = 3k - m
-8 = -2k + 4m

lalu kita eliminasi
7 = 3k - m |×4|
-8 = -2k + 4m |×1|

28 = 12k - 4m
-8 = -2k + 4m
——————— +
20 = 10k
k = 2

lalu kita substitusi
7 = 3k - m
7 = 3(2) - m
7 = 6 - m
7 - 6 = -m
1 = -m
m = -1

maka,
k + m = 2 + (-1)
k + m = 2 - 1
k + m = 1

semoga membantu, mohon dikoreksi bila ada kesalahan