Solve each equation mentally

Answer:
Step-by-step explanation:
a) 2x = 10
Divide both side by 2
x = 10/2
x = 5
b) -3x = 21
Divide both sides by (-3)
x = 21/(-3)
x = -7
[tex]c) \frac{1}{3}x = 6[/tex]
Multiply both sides by 3
x = 6*3
x = 18
[tex]d)\frac{-1}{2}x = -7[/tex]
Multiply both sides by (-2)
x = -7 * (-2)
x = 14