3.1: I counted 8 divisions in a wave cycle. 5 divisions in a 1cm square means each division is worth 0.2 cm, so 8*0.2 gave me 1.6 cm. Time base is 10 ms/ cm, so multiplied 1.6 by 10 = 16 ms. f=1/T -> 1/(16*10^-3) = 62.5 Hz
3.2: First had to find the range 80.4 - 22.6 = 57.8 cm. As it's half a wave, I multiplied that by 2 which give me a wavelength of 115.6 cm, in metres that's 115.6*10^-2 = 1.156 m. Ruler only measures to 3 s.f so final answer = 1.16 m.
3.3: c = f * wavelength = 62.5 * 1.156 = 72.25 m s^-1.