I assume you want the expression to this so it would be x-y-3
<LMP and <NMP are supplementary angles so sum = 180
<LMP + <NMP = 180
(-16x + 13) + ( - 20x + 23) = 180
-16x + 13 - 20x + 23 = 180
-36x + 36 = 180
-36x = 144
x = -4
<LMP = -16x + 13 = -16(-4) + 13 = 77
<NMP = - 20x + 23 = - 20(-4) + 23 = 103
Answer
<LMP = 77°
<NMP = 103°
I don't know about the first one but for the second one:

Step-by-step explanation:
- 3x+5y=7b equation 1
- 2x+4y=1
2x=-4y+1
- x=(-4y+1)/2
- x=(-4y+1)/2 in equation 1
3×(-4y+1)/2+5y=7b
(-12y+3)/2+5y=7b
(-12y+3+10y)/2=7b
(-12y+3)/2=7b
-12y+3=14b
-12y=14b-3
- y=3-14b/12
- y=3-14b/12 in x=(-4y+1)/2
x=(-4×{3-14b/12}+1)/2
x=(-3+14b)/3+1/2
x=14b/3×1/2
223
-119
104
In stead of doing 3-9 and 2-1 do 23-19 then 2-1