translate this expression into a mathematical problem

the difference between one more than three times a number and a number is 19 find the smaller number

2 answers

| (3 n +1) - n | = 19
note difference can be + or -

if +
2 n = 18
n = 9

if -
-2n = 18
n = -9
oops. |2n+1| = (2n+1) or -(2n+1)

if -(2n+1) = 19
-2n = 20
n = -10

check:
|(3(-10)+1-(-10)| = |-30+1+10| = |-19| = 19