Pretty damn simple man. Equilibrium=box no move. Four things you need to figure out: Weight of box (W): m(mass of box) • g (acceleration due to gravity) Normal force (Fn): W • sin(60) Force of friction (f): Fn•us (static coefficient of friction) Minimum magnitude of applied force created equilibrium (F): W• cos(60) - f A) F = 5.1 B) Fn = 17 Took me longer to write this than it did to figure out those values. These problems are super easy if you split it up into component vectors. We know the mass of the box, so automatically we can figure out the force gravity is doing, as F = ma. From their, we know the normal force is perpendicular to the surface of the incline, so if we are to set the incline as 0° along the x-axis, the normal force is going in the direction of the y-axis, or 90°. Simple geometry tells us that the angle of the incline is the same as the angle the weight creates with from the y-axis on our arbitrary plane. So thus, we treat weight as the hypotenuse, and the normal force is weight • the sin of the incline's angle. Maximum force of static friction (be careful, you may not always be using the maximum, however since the box is in equalibrium, and we are looking for the minimum force to keep it there, we want the maximum static friction force.) is just the normal force • static coefficient. Now be conscious that the weight is not perpendicular to the incline, so that means there is an x-component of the weight that influences the box. Just like we found the normal force, but for the other side, weight • cos of the incline's angle. Now, since the box is not moving we need the forces on either x-side to cancel out. Since the x component of weight will be in the direction of the only force that would be doing work on the box if the applied force wasn't there, it will be in the direction of the motion. So we must set the forces going in the negative x direction (weight x-component) equal to the forces going in the positive x direction (friction and the applied force). Wx= f + F Since we need the applied force Wx - f = F.