We first note that there is a useful relation between a, b, d, and v. The total number of integers on the two pieces of paper is a+b, the number of integers on Alicia's piece of paper plus the number of integers on Britt's piece of paper. This, however, also equals v+d: the total number of distinct integers, plus the total number of integers that have been written down twice. Hence, we get that a+b=v+d.
a. We choose a=b=2022 and look for a solution to a⋅b=d⋅(v+d). We use the fact that a+b=v+d. This means that we are looking for solutions to a⋅b=d⋅(a+b). If we substitute a=b=2022, then we find that 2022⋅2022=d(2022+2022)=d⋅2⋅2022, so d=1011. Together with a+b=v+d, we find that 2022+2022=v+1011, so v=3033. This situation happens for example if Alicia writes down the numbers 1 to 2022, and Britt writes down the numbers 1012 to 3033.
b. With a little bit of trying, and by choosing d not too large, we find that a=b=3, d=1, and v=5 is a solution: 3⋅3=1⋅(5+4). The numbers also satisfy the equation a+b=v+d. This situation can occur if Alicia writes down the numbers 1, 2, and 3, and Britt writes down the numbers 3, 4, and 5, for example.
c. Suppose that there are numbers such that a⋅b=v⋅d. We already deduced that a+b=v+d, or v=a+b−d. Substituting this yields
ab=vd=(a+b−d)d=ad+bd−d2.
If we now subtract ad from both sides of this equation, we find ab−ad=bd−d2, so a(b−d)=d(b−d). Because Britt wrote down at least one number that Alicia did not write down, we have b>d. Therefore, we can divide the equation a(b−d)=d(b−d) by the positive number b−d, and we find that a=d. On the other hand, Alicia wrote down at least one number that Britt did not write down, hence a>d. This gives a contradiction and hence there cannot exist numbers such that a⋅b=v⋅d.