The standard way to solve this Atwoods problem is to do a force balance on each object assuming the "+direction" is down for the hanging mass and up the hill for the mass on the incline.
The Force balance on the mass on the incline (let's call it m2) is T - m2gsinθ - m2gcosθ = m2a
The Force balance on the hanging mass(m1) is m1g - T = m1a
Add these two equations and solve for a which is the same for the attached masses.
In order to find T, substitute the a that you find into the hanging mass force balance and solve for T.
Good luck!