The number of boys and girls in a school is 280 and 340

147       138        120       93       ?       12

Complete the series choosing the missing number.

8, 13, 20, ____, 40.

48      61       76       94     116       ?

? + (55)² = (140)² – (80)² – 6278

0       2       10        24          68          120

520    79    440    151     376     ?

100     180      294      448      648      ?

0        2          6        12         20          ?

6, 17, 21, 47, ?, 107

Select the number from among the given options that can replace the question mark (?) in the following series.

64, 60, 52, 40, ?, 4