Answer:
6 1/6 (i think )
substitute 4 in for a, -5 for b and -7 for c
(4+ 2 * - 7 * - 5)/3 * 4
3*4 = 12
4+2 * - 7 * - 5) / 12
-7 * - 5 = 35 (same sign so positive)
(4+ 2* 35)/12
2*35 = 70 and 70+4 = 74.
74/12 is what we have, and we can simplify this to 37/6 by dividing both the numerator and denominator by 2. now we convert to mixed fraction and get 6 1/6.
Explanation: