Jessa completed a 50-mile bicycle race in 4 hours. After the race, she realized that the air pressure in her tires was low, which slowed her down by an average of 2 miles per hour. She wants to solve the equation below to find r, her average speed in miles per hour with properly inflated tires,
4(r - 2) = 50

Long division setup showing an incomplete calculation. 12 is in the divisor, 6839 is in the dividend, and 5 hundreds and 6 tens is written in the quotient. 6000 is subtracted from 6839 to give 839. an unknown value represented by a box is being subtracted from 839. what number should be placed in the box to complete the division calculation?