Tentukanlah pengurangan 15a +7b -5c oleh -11a -12b +13d#mohon di bantu

-11a – 12b + 13d – (15a + 7b – 5c)
= -11a – 12b + 13d – 15a – 7b + 5c
= -11a – 15a – 12b – 7b + 5c + 13d
= -26a -19b + 5c + 13d