Tina, Dawn & Harry have $175 together. Tina has 3x as much as Dawn. Dawn has 2x as much money as Harry. How much money does each have?
Let $\displaystyle T,\,D,\,H$ represent the amount of money Tina, Dawn, and Harry have respectively.
So we know that
$\displaystyle T+D+H=175$ -- (1)
$\displaystyle T=3D$ -- (2)
$\displaystyle D=2H$ -- (3)
Subbing (3) into (2), we can see that
$\displaystyle T=6H$ -- (4)
Now substitute (4) and (3) into (1) to get
$\displaystyle 6H+2H+H=175\implies 9H=175\implies H=19.44$
Thus, $\displaystyle T=6(19.44)=116.64$ and $\displaystyle D=2(19.44)=38.88$
(Note that when we go to check our answer, we have $\displaystyle 19.44+38.88+116.64=174.96\approx175$ due to rounding errors.)
Does this make sense?
Are you sure you have copied the problem exactly? Although I can solve this, the end result does not divide evenly. If they had 175.50 together, then each would have an evenly dividable amount.
But, going with what you wrote:
Let x = Harry's money
2x = Dawn's money (since Dawn has 2 times as much money as Harry)
3(2x) = Tina's money (Tina has 3 times as much as Dawn)
All together they have $175.
x + 2x + 3(2x) = 175
Collect like terms on the LHS, then divide both sides by the coefficient of x. That will solve for x, which is Harry's money. Then multiply x by the right amounts to calculate Dawn and Tina's money.