Let x = the number.
"increased by" tells you we are adding.
"twice a number" tells you 2 times a number.
16 + 2x = - 24
Subtract 16 from both sides so that we have the variable on one sides and the constants on the other.
2x = - 24 - 16
2x = - 40
Divide by 2 to isolate the variable.
x = - 40/2 = - 20
Your solution is - 20.
To check your answer, plug in.
16 + 2(-20) = - 24
16 - 40 = - 24
- 24 = - 24