Solve using the substitution method 3m-n=18 and 2m+n=-7

m = 11/5, n= -57/5

Step-by-step explanation:

3m-n=18 and 2m+n=-7

Solve one of the equations for n

2m +n = -7

Subtract 2m from each side

2m-2m +n = -7 -2m

n = -7-2m

Substitute this into the first equation

3m -n =18

3m - (-7-2m) = 18

Distribute the minus sign

3m +7+2m = 18

Combine like terms

5m +7 = 18

Subtract 7 from each side

5m+7-7 = 18-7

5m = 11

Divide by 5

m = 11/5

Substitue this back into the equation for n

n = -7-2m

   =-7 -2(11/5)

   =-7-22/5

   -35/5 -22/5

  =-57/5

Angle A is opposite to BC

Step-by-step explanation:

Just look at the figure, what is opposite to what, can't give a better explanation