linearly: 8560 bacteria
exponentially: approximately 75233 bacteria
assuming it is not exponential (we would have some really complicated logarithms), let's say it is linear. then, after 5 hours, it increased by 1200 bacteria, so every hour it increases by 240 bacteria. this means that after 19 hours, we get 19 * 240 + 4000 bacteria or 3800 + 760 + 4000 = 7800 + 760 = 8560 bacteria.
because it says round your answer, i will do this exponentially (with a calculator, of course). first, we need to find how much it multiplies by every hour, by taking the 5th root of 52/40 or 13/10. this is approximately 0.167. we still need to add 1 to this, because we are multiplying by that number, not adding that amount of the number. now, we just calculate 4000 * (1.167)^19. use a calculator to get approximately 75232.6, or 75233.
5x - 9 = 2x + 23
this question is asking you to take a verbal description to write an equation. using key words and phrases from the problem, you can set up an equation and solve for the missing variable.
'five times a number': 5x (5 multiplied by a variable)
'decreased by 9': -9 (subtract 9)
'five times a number decreased by 9': 5x - 9
'is equal to' =
'twice the number': 2x (2 multiplied by the variable)
'increased by 23': + 23 (add 23)
'twice the number increased by 23': 2x + 23
set the two expressions equal to each other: 5x - 9 = 2x + 23
The (greatest, least) of the common f...