Help please with these questions

[KhadijahA-R]

(5 [60] 9) (7[71] (6 [?] 15) Answer should be 105
(24[51]18) (27[60]24) (17[?]28) Answer should be 54

Completely stumped by these, all help would be appreciated
Many thanks

[ToadMum]

(5 [60] 9) (7[71] (6 [?] 15) Answer should be 105
(24[51]18) (27[60]24) (17[?]28) Answer should be 54

Completely stumped by these, all help would be appreciated
Many thanks

(5 [60] 9) (7[71] (6 [?] 15)
First number*second number, add 15 = middle number

(24[51]18) (27[60]24) (17[?]28)
(First number + second number) + 9 = middle number

[KhadijahA-R]

(5 [60] 9) (7[71] (6 [?] 15) Answer should be 105
(24[51]18) (27[60]24) (17[?]28) Answer should be 54

Completely stumped by these, all help would be appreciated
Many thanks

(5 [60] 9) (7[71] (6 [?] 15)
First number*second number, add 15 = middle number

(24[51]18) (27[60]24) (17[?]28)
(First number + second number) + 9 = middle number

Thankyou, I just couldn't see it
I keep thinking the adding of another number at the end must come from amongst the trio of numbers, i.e. must be either A or C when (A C), but I see it can be a random, just has to be applied in the same way .