Help please how do i do this

m<A = 39

Step-by-step 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