What is the difference between tax credits and tax deductions?

Tax credits reduce the amount of income tax, a person owes to the federal and state governments. It is a type of tax incentive that is subtracted from the total tax he has to pay.

Tax deductions are certain deductions that a person can get in order to lower his tax liability. These deductions are in the form of expenses from the whole year, like insurance premiums or any form of charity etc. These expenses are subtracted from the gross income to get the amount of tax owed.

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.