Write a two-step equation involving division and addition that has a solution of x=25

If this is what you mean..?

In order to do this you would work backward from the answer.
You have x = 25 and ant to include and addition. As we are working backwards, we use the opposite operation to addition - subtraction. We'll make it an easy number so we will subtract 15 to get to 10.
So far it looks like 10 = 15 + x
Now, to include  a division, we want to do the opposite again, multiplication. Pick any number to multiply 10 by - for this example we'll choose 7.
7 x 10 = 70
Now we can write out the equation -
70/7 + 15 = x
No brackets are required as Division comes before addition in BIDMAS.

An alternate choice would be to have x the other side of the '='

To do this, multiply x by a number of choice (for example 3) to make the divison section of the equation. This makes 75. This can be written as a fraction. 75/x = 3
Next, for the addition, whatever happens on one side, the exact same happens on the other. Pick any number to add on (e.g. 5) and re-write the equation.
75/x + 5 = 8

Sorry if this doesn't make perfect sense

The answer is 225 miles per 4.5 hours. hope this ; )