Two-Sided Frequency Spectrum
First of all, you should totally fix the $x$-axis :)

Now, as you only have two sine waves, you should expect to have peaks at their exact frequencies (that is, at $\pm 60\textrm{ Hz}$ and $\pm 100\textrm{ Hz}$). The FFT function in MATLAB gives you the Discrete Fourier Transform of your signal within $0$ and $F_s$, where $F_s$ is your sampling frequency -and given that you represent your signal with samples, even if you are not aware of it, you have one. Anyway, to make visualization easier, we focus on the interval $[-\frac{F_s}{2},\frac{F_s}{2}]$; that way, your spectrum will be centered around the $0$ frequency -use the function fftshift for that. So, now, once you fix the $x$-axis according to your sampling frequency, you will find that the peaks are at the frequencies you have defined for your sine waves.

When it comes to the little ripples in the lower part of your spectrum, that's just disturbance caused by the noise. Since you are adding noise to the signal by the randn function, your noise follows a Gaussian distribution, translating into white noise for your signal. That is why your entire spectrum is showing sings of being slightly disturbed.

By the way, after fftshift, just get rid of the first half of your vector and you'll end up with positive frequencies.