4 4 4 4 20 use - or obleaque?

just multiply 4 times 5=20

No sign of operation was mentioned. In other words, 4 4 4 4 4 4 here equals 444,444 and that should be that. If there is a common sign of operation, like "x" for "times" then it's 4 x 4 x 4 x 4 x...

A 4-4-4-4 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, has a four-wheel leading truck, two sets of four driving wheels, and a four-wheel trailing truck

4! + 4 - 4 - 4. The ! represents factorial ie 4 x 3 x 2 x 1 so we have 24 + 4 - 4 - 4 = 20

4_4_4_4 = 204/4+4*4=204/4 =1+4=5*4=20