We’ll use x to represent the mystery number.
“Sixteen less than” means subtraction, so we have 16 -
“Less than a number” simply means 16 - x
“Equals - 19” sets 16 - x equal to -19. In other words, 16 - x = -19
To solve, we subtract 16 to get x alone:
-x = -35
Divide the entire equation by -1 to make x positive:
-1(-x = -35) leaves us with x = 35