Barbara is converting 78°f to degrees celsius. first, she subtracts 32 from 78.

a.) multiply 46 by 5/9
b.) multiply 46 by 9/5
c.) add 273 to 46
d.) subtract 273 from 46

When converting temperature from fahrenheit to celsius scale the following formula is used
(temperature in fahrenheit  - 32) x 5/9 = temperature in celsius 
the temperature has been given in fahrenheit , we need to convert it to celsius
the first step has already been given 
step 1 - 
78 °F - 32 = 46 
step 2 - 
we have to multiply 46 by 5/9
the correct option is A)multiply 46 by 5/9

The best and most correct answer among the choices provided by your question is the first choice or letter A. For Barbara to convert 78F to Celsius. She must subtract 32 from 78. then multiply it by 5/9.
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The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.