a/4x-15=-75-x

⇔4x+x=-75+15

⇔5x=-60

⇔x=-12

vậy x=-12

b/

72-3x=5x+8

⇔72-8=5x+3x

⇔64=8x

⇔x=8

vậy x=8

c/

-7|x+3|=-49

⇔|x+3|=7

⇔[x+3=7x+3=−7[x+3=7x+3=−7 ⇔ [x=4x=−11[x=4x=−11 

vậy x=4 hoạc -11

d/

-8x+12=-5x-33

⇔-8x+5x=-33-12

⇔-3x=-45

⇔x=15

vậy x=15