13) (p)/(2)+6=3 15) 1=(x)/(6)+2 17) (-7+k)/(20)=-1 19) -10+3a=2

## Step 1: Isolate the term with 'p'<br />### Subtract 6 from both sides of the equation: $\frac{p}{2} + 6 - 6 = 3 - 6$. This simplifies to $\frac{p}{2} = -3$.<br /><br />## Step 2: Solve for 'p'<br />### Multiply both sides by 2: $2 \cdot \frac{p}{2} = 2 \cdot (-3)$. This simplifies to $p = -6$.<br /><br />## Step 3: Isolate the term with 'x'<br />### Subtract 2 from both sides of the equation: $1 - 2 = \frac{x}{6} + 2 - 2$. This simplifies to $-1 = \frac{x}{6}$.<br /><br />## Step 4: Solve for 'x'<br />### Multiply both sides by 6: $6 \cdot (-1) = 6 \cdot \frac{x}{6}$. This simplifies to $x = -6$.<br /><br />## Step 5: Isolate the term with 'k'<br />### Multiply both sides by 20: $20 \cdot \frac{-7 + k}{20} = 20 \cdot (-1)$. This simplifies to $-7 + k = -20$.<br /><br />## Step 6: Solve for 'k'<br />### Add 7 to both sides: $-7 + k + 7 = -20 + 7$. This simplifies to $k = -13$.<br /><br />## Step 7: Isolate the term with 'a'<br />### Add 10 to both sides of the equation: $-10 + 3a + 10 = 2 + 10$. This simplifies to $3a = 12$.<br /><br />## Step 8: Solve for 'a'<br />### Divide both sides by 3: $\frac{3a}{3} = \frac{12}{3}$. This simplifies to $a = 4$.