I need help with this asap

If Samuel can type 40 words per minute, he can type [tex] 40m [/tex] words in [tex] m [/tex] minutes. So, the amount of minutes you're interested in is the solution of the equation
[tex] 40m = 3.5 \times 10^5 \iff m = \dfrac{3.5 \times 10^5}{40} = \dfrac{3.5 \times 10^5}{4\cdot 10} = \dfrac{3.5}{4} \times 10^4 = 0.875\times 10^4 = 8750 [/tex] minutes.
Since 8750/60 is 145 with reminder 50, Samuel can type the required amount of words in 145 hours and 50 minutes.