Find 4 positive consecutive even integers such that the third times the fourth is twenty one times the first

Consecutive means in order, so like 1,2,3,4... or 14,15,16,17...

consecutive even means 2,4,6,...

now, first you define some variables

let "a1"  be the first positive even integer

well, you could define a2,a3,and a4 to be the next consecutive even integers but you actually dont need to
because the next consecutive even integer is
a1+2

the 3rd is
a1+2+2

and the 4th is
a1+2+2+2=a1+6

now, looking at the problem it states the "third" times the "fourth" is equal to 21 times the "first"

putting it into equation form

(a1+4)* (a1+6)= 21*a1

solve for a1, and then it should be easy to determine the rest of the positive consecutive even integers