Bonjour,
a. 1/3 + y = -2/6
1/3 - 1/3 + y = -2/6 - 1/3
y = -2/6 - (1 * 2)/(3 * 2)
y = -2/6 - 2/6
y = -4/6
y = (-2 * 2)/(3 * 2)
y = -2/3
b. 8/7 = -x / 5
8/7 * 5 = (-x / 5) * 5
(8 * 5)/7 = -x
40/7 = -x
x = -40/7
c. 3t + 4 = -2 (1 - t) - 6
3t + 4 = -2 * 1 - 2 * (-t) - 6
3t + 4 = -2 - (-2t) - 6
3t + 4 = -2 + 2t - 6
3t - 2t = -2 - 6 - 4
t = -12
