50+5x=total profit. To get 10% of 50 you would multiply .1x50= 5. X would be the amount of days past so 10th day = $100 total but $50 profit and 30th day = $200 total but $150 profit
The work is incorrect.
(-6) multiplies both terms inside parentheses. For some reason, the student changed the sign of that multiplier for the second term. The second term of the result should have a positive sign, the result of multiplying (-6)(-2/13) = +12/13.
If you had a fair coin, the probability of seeing heads is 1/2, meaning you’d see heads 30 times