1) F3 = F1+F2
F4 = F2+F3 = F2+F1+F2 = F1+ 2F2
F5 = F3+F4 = F1+F2+2F2+F1 = 2F1+ 3F2
F6 = F4+F5 = 2F2+F1+2F1+3F2 = 3F1+ 5F2
F7 =F5+F6 = 2F1+3F2+3F1+5F2 = 5F1+ 8F2
F8 = F6+F7 = 8F1+13F2
F9 = 13F1+21F2
F10 = 21F1+34F2
2) 7335+11733=19068=F18 (this is not part of the "true" Fibonaccci series, where F16=987, F17=1597)
3) F23=28657, F25=75025=28657+F24, F24=75025-28657=46368
(Point of interest: the Fibonacci series is closely connected to the Golden Ratio,G=(1+√5)/2=1.618 approx. To find the next term following a given one, multiply by G and round it up to the nearest integer. The bigger the term the closer the product will be to an integer. F23=28657. F23*G=46368.00002 approx, so F24=46368 and F25=F24*G=75024.99999 approx, so F25=75025.)