One of the triangles (that on the left, top) has 2 equal sides, and thus is isosceles. The angle immediately adjacent to and to the right of 110 degrees is 180-110 degrees, or 70 degrees, which means that angle 1 is also 70 degrees. The remaining angle is 180 degrees less 2(70 degrees), or 40 degrees; thus, angle 2, immediately adjacent to and to the right of this 40 degree angle, is 180-40, or 140 degrees. The triangle to the right and below the horiz. line has angle 40 degrees (using the principle of vertical angles); thus, angle 3 is 180-(40+90) degrees, or 50 degrees.
The present value of an annuity is given by

where: PV is the current value of the annuity, P is the periodic payment, r is the apr, t is the number of compounding in one year and n is the number of years.
Thus, given that PV = $51,800; r = 7.8% = 0.078; t = 12; n = 4.

Therefore, the <span>monthly payment is $1,259.73</span>
Can you explain the question in words please?