To find the amount of Social security tax deducted from Martha’s gross pay, we just need to find the 6.2% of $1,215.60. To do it we are going to convert the tax from percentage to decimal form, and then we'll multiply the resulting decimal by her gross pay.
Now, to convert the social security tax from percentage to decimal form, we are going to divide the percentage 6.2% by 100%:

The only thing left now, is multiply Martha's gross pay by the Social Security tax in decimal form:
Social Security tax deducted = (0.062)($1,215.60) = $75.3672 which rounds to $75.37
We can conclude that the correct answer is c. $75.37