If a slide is being viewed with the high power objective which adjustment knob should be used to sharpen the focus

Once it is grossly in focus, use the fine adjustment knob to sharpen the focus. Move the nosepiece to medium power. Only use the fine adjustment knob for medium and high power. the objective lens is switched to the lowest-power magnification.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.