I'm not sure if the problem is (2/3)(3x+1) or 2/[3(3x+1)]? I'll solve both:
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(2/3)(3x+1) = 5
Multiply both sides by 3/2:
3x + 1 = 15/2
Subtract 1 from both sides:
3x = 13/2
Divide both sides by 3:
x = 13/6
Check:
(2/3)(3x+1)
(2/3)(3(13/6)+1) = 5
(2/3)(45/6) = 5
90/18 = 5
5 = 5 Check!
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2/[3(3x+1)] = 5
Multiply both sides by (3x+1):
2/3 = 5(3x+1)
Divide both sides by 5
2/15 = 3x + 1
Subtract one from both sides:
2/15 - 1 = 3x
2/15 - 15/15 = 3x
-13/15 = 3x
Divide both sides by 3:
-13/45 = x
Check:
2/[3(3x+1)] = 5
2/[3(3(-13/45)+1)] = 5
2/[3(6/45)] = 5
2/(18/45) = 5
2*(45/18) = 5
90/18 = 5
5 = 5
Check!
