To solve this equation, we can start by simplifying each side of the equation separately.

On the left side, we have 5^2, which is equal to 25.

On the right side, we have 3^18 + 2^8. To simplify this, we need to calculate each exponent separately.

3^18 is a very large number, so it may be difficult to calculate it exactly. However, we can use a calculator to find an approximate value. 3^18 is approximately equal to 387,420,489.

2^8 is equal to 256.

Now we can rewrite the equation with the simplified values:

25 = 387,420,489 + 256

Now we can solve for the unknown variable (in this case, there is no unknown variable, but we can still simplify the equation further):

25 = 387,420,745

Since 25 is not equal to 387,420,745, the equation is not true. Therefore, there is no solution to this equation.