document.write( "Question 726592: Fill in the blank with the appropriate problem number 18,19 or 20 and then give the solution. \n" );
document.write( "Problem 21 can be solved with the setup given in problem_______and the solution to problem 21 is? \n" );
document.write( "Problem 22 can be solved with the setup given in problem_______and the solution to problem 22 is? \n" );
document.write( "Problem 23 can be solved with the setup given in problem________and the solution to problem 23 is?\r \n" );
document.write( "\n" );
document.write( "18)26*26*26*26(counting principle)? \n" );
document.write( "19)900C10 (combination)? \n" );
document.write( "20)90!/(90-10)!*10!(counting principle, combination,factorial,permutation)? \n" );
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