The first term is -43.
Explanation:
an = a + (n - 1)d
a12 = a + 11d = 56, first equation
a21 = a + 20d = 101, second equation
Subtract the second equation from the first equation, cancelling +a and -a
11d - 20d = 56 - 101
-9d = -45
d = 5
Subtitute d into the first equation
a + 99 = 56
a = -43
a refers to the first term, hence the first term is -43.
The complete question in the attached figure
we know that
m∡4=65°
m∡4=m∡2---------> by internal alternate angles
m∡5=m∡3---------> by internal alternate angles
m∡1=180°-m∡2---------> 180°-65°--------> m∡1=115°
the answer is
m∡1=115°
-- Find how much 'y' changes from the first point to the second one.
-- Find how much 'x' changes from the first point to the second one.
-- The slope of the line going from the first point to the second one is
(change in 'y') / (change in 'x') .