How to write 50,000 using exponents

50,000 = 5 x 10,000 but 10,000 = 10 x10 x 10 x 10  
You know that the exponent of any number (even if it's not shown) is 1, then:

10 x 10 x 10 x 10 = 10¹ x 10¹ x 10¹ x 10¹ = 10⁴ (remember a³ x a⁴ = a³⁺⁴ a⁷)

then 50,000 = 5 x 10⁴