Write the sentance as a equation. use x to represent "a number" six subtracted from a number equals 42

Hey there :)

We have been given a variable x to represent the unknown number

The sentence is:
six subtracted from a number equals 42

The first number in subtraction is called Minuend
And the number that is after the minus sign is called Subtrahend

Since 6 is being subtracted from, the equation will be

[ x - 6 = 42 ]

Extras 
x - 6 = 42
x = 48

3were boys and 5 were girls