5^4x+3/25^9-x

 Answer: 5 

Step 1: Should have the same base to use the exponent rule.

Step 2:  We get 5^6x-15. 

Step 3: 5^6x-5 = 5^2x+5 combine like terms. 

Step 4: you will get x = 20 /4 x= 5.