Answer:
m<A = 39
Explanation:
1. Approach
To solve this problem, one first has to find the value of "x", then one will substitute "x" back into the equation given for the value of m<A, to solve for m<A. In order to solve this problem, one has to know that the sum of angle measures in a triangle will always equal 180.
2. Solving for "x"
The sum of angle measure in a triangle will always equal 180 degrees, hence one can set up an equation,
m<A + m<B + m<C = 180
Substitute,
(10x - 1) + (18x + 2) + (15x + 7) = 180
Simplify,
43x + 8 = 180
Inverse operations,
43x + 8 = 180
-8 -8
43x = 172
/43 /43
x = 4
3. Solve for m<A
Now all one has to do is substitute the value of "x" back in to solve for m<A
10x - 1
x = 4
10(4) - 1
40 - 1
39