If you have 4 values, and R is their average, then 4R is their sum, from the definition of an average (just rewrite average = sum/n so you have 'sum' on one side).

So here, 4R(1) is the sum of the four values in row 1, 4R(2) is the sum of the four values in row two, and so on, and thus 4[ R(1) + R(2) + R(3) + R(4) + R(5) ] will be the sum of all twenty values in the spreadsheet, and statement 1 is sufficient (the sum is 4*550 = 2200, and we can divide that by 20 to find the average value).

Similarly, 5C(1) will be the sum of the five values in column 1, and so on, so 5[ C(1) + C(2) + C(3) + C(4) ] is the sum of all twenty values in the spreadsheet, and Statement 2 is sufficient (the sum is 5*440 = 2200, and we can divide that by 20 to find the average value).