Estimate : 23 × 67
20 (lower down, lower than 5...the last digit) × 70 (Higher, higher than 5)
=20×70
=1400
The estimated value will be 1400
An easy way to think of independent and dependent variables is, when you're conducting an experiment, the independent variable is what you change, and the dependent variable is what changes because of that. You can also think of the independent variable as the cause and the dependent variable as the effect.
I hope this helps!