To solve this equation, we can start by simplifying the left side:

20%.x - (-3/10) = -25%

Since 20% is equivalent to 0.2, we can rewrite the equation as:

0.2x + 3/10 = -25%

Next, we can subtract 3/10 from both sides to isolate the variable:

0.2x = -25% - 3/10

To combine the percentages and fractions, we need to convert them to a common denominator. The common denominator for 25% and 3/10 is 100, so we have:

0.2x = -25/100 - 30/100

Simplifying the fractions:

0.2x = -55/100

Now, we can simplify the right side by dividing both the numerator and denominator by 5:

0.2x = -11/20

Finally, we can solve for x by dividing both sides by 0.2:

x = (-11/20) / 0.2

Dividing the numerator by 0.2:

x = -11/20 ÷ 0.2

x = -11/20 * 5/1

x = -55/20

Simplifying the fraction:

x = -11/4

Therefore, the solution to the equation is x = -11/4.