a) 7x+4 < -2x+1
7x+2x < 1-3
9x<-2
x<-2/9
b) 2x-3 > 6x+4
2x-6x>4+3
-4x>7
x> -7/4
c) 3/4x <= 0
x <= 0 * 4/3
x <= 0
d) -5x >= 1/4
x >= 1/4 * -5
x >= -5/4
e) (x+3)/-2 >= 0
-x/2 -6 >=0
-x/2>=6
-x>=6*2
x>= -12
f) (2x+7)/5 <= (x-9)/4
2x/5+7/5<= x/4-9/4
2x/5-x/4<= -9/4-7/5
8x/20-5x/20<= -45/20-28/20
3x/20<=-73/20
3x<= -73/20*20
3x<= -73
x<= -73/3