1/x=(5/7)(1/4)

1/x= 5/28

x=28/5

3a/7=-2/5

3a=(-2/5)(7)

a=(-14/5)(1/3)

a= -14/15

24/x-3=72/x+3

(x+3)(24/x-3)=(72/x+3)(x+3)

24x+72/x-3=72

(24x+72/x-3)(x-3)=(72)(x-3)

24x+72=72x-216

24x+72+216=72x-216+216

24x+288=72x

24x-24x+288=72x-24x

288=48x

6=x

x= 6

4 = 5x/7 Next, multiply each side by 7, so,

28 = 5x Next, divide each side by 5, so,

28/5 = x.

2] 3a/7 = -2/5 First, xly each side by 7, so,

3a = -14/5 Next, xly each side by 5, so,

15a = -14, Next, divide each side by 15, so,

a = -14/15.

3] 24/[x-3] = 72/[x+3] 1st step, xly each side by [x-3],so

24 = 72[x-3]/[x+3], Next, xly each side by [x+3], so

24[x+3] = 72[x-3], Next, expand the brackets, so

24x+72 = 72x-216, Next, add 216 to each side, so

24x+288 = 72x, Next, take 24x from each side, so

288 = 48x, Next, divide each side by 48, so

6 = x. Hope this helps, Twiggy.