Let a=number of pens and b=number of pencils.
8a+7b=3.37; 5a+11b=3.10.
To eliminate a variable multiply the first eqn by 5 and the second by 8:
40a+35b=16.85, 40a+88b=24.80.
Subtract these equations: 53b=7.95, b=$0.15. So 5a=3.10-1.65=$1.45, a=$0.29.
Pens are $0.29 each and pencils $0.15.
Answer:
-8
Step-by-step explanation:
using the law of cosines:
a^2 = b^2 + c^2 - 2*b*c*cos(A)
a = 90, b = 55, c = 50
90^2 = 55^2 + 50^2 - 2*55*50*cos(A)
8100 = 3025 + 2500 - 5500 * cos(A)
5500 * cos(A) = 3025 + 2500 - 8100
5500 * cos(A) = -2575
cos(A) = -103/220
A = arccos(-103/220)
A = 117.9 degrees
