How do I solve “twice as large as 985-670

I suggest that you use concrete numbers at first to set up the equation or expression. Once you are able to see how the numbers are put into place then you can substitute out the numbers for variables where necessary .  In this case you should make the variable the smaller number.  Lets say that the first number is a  3 , then the second number would be 3 2= 6. If you decided to use variable we would say that x =3 so x 2 =6. So your expressions would be x and 2x.

Option: D is the correct answer.

D.Multiply each side by −5, add 25 to each side

We are given an algebraic expression in terms of variable x as follows:

Now, firstly we will multiply both side of the equation by -5 to get:

Now we add both side of the equation by 25 to get: