Question

write an expression for the calculation double 7, multiply 3 and 1 and then subtract the second number from the first number

Answer 1

14(3+1) - (3 - 7)

"double" - times by 2
"and" - addition
when using " first second and third" you just have to assign the numbers by the way it comes in the problem...
first number - 7
second number - 3
third number - 1