Exercise punch samsung

What's the formula to find the y intercept for a straight line using xy coords? - coords in clansphere

Hello,
I use y = mx + c formula, and all I have are the two values of x and y (-1.1) and (0.3). Maybe someone would tell me, step by step, how you doing? I try again to learn more math after school for a few years than twenty, and only need the basics since then.

Thanks
David