Question

last month,a factory produced 800 television sets. This month, the same factory produced 1,064 t.v. sets the increase in production from last month to this month is?

Answer 1

This is a simple subtraction problem.
1064 - 800 = 264

Answer 2

If you're looking for a percent, then
264 / 800 = 33/100, so a 33% increase.