It's a little unclear as to what you have, but.....I'll give it a shot :
-4=4sin([360/70](x-12.5))-2 add 2 to both sides
-2 = 4 sin [(36/7)x - 450/7] divide both sides by 4
-1/2 = sin [(36/7)x - 450/7]
The sin = -1/2 at 210° and at 330°
So solving
(36/7)x - 450/7 = 210
36x - 450 = 1470
36x = 1920
x = [160/3]° ≈ 53.333°...... with the 3s repeating
And solving
(36/7)x - 450/7 = 330
36x - 450 = 2310
36x = 2760
x = [230/3]° ≈ 76.666°....... with the 6s repeating
The more general solutions......as shown by this graph...... https://www.desmos.com/calculator/gh9a73uifc ..... are
x = [160/3]° + n*70° where n is an integer and
x = [230/3]° + n*70° where n is an integer
