The pattern follows subtracting consecutive integers: 124-19=105, 105-18=87, but then 87-17=70, not 75. The number 87 breaks the pattern; it should be 88 to maintain the sequence (124-19=105, 105-18=88, 88-17=71, 71-16=55, 55-15=40) or 75 should be 70.