Two steps:

1) Bring the 7 to the opposite sides. To do this, subtract 7 from both sides. You get 5r - 7 = 9t.

Explanation: The first thing you ever do to solve for a variable is look for "constants" or numbers that don't have a variable attached to them. You have to make sure that the number is not on the side of the variable which you're solving for. In our example, 7 was on the side of t. Since we're solving for t, we have to move 7 to the other side.

2) Get rid of the number attached to t (9). To do this you would divide both sides by 9. You get (5r - 7) / 9 = t.

Explanation: After you move everything that's not attached to your wanted variable (like 7 in our example) you have to get rid of whatever is attached to that variable to get it by itself. In our example we had 9t left over. We needed to get rid of the 9 that was attached to it to get t by itself. To do this we divided by the "coefficient" or attached number. In our case we divided both sides by 9.

The final answer is (5r - 7) / 9 = t.