Evaluate: 15=1-(x)/(3)

Expression: $15=1-\frac{ x }{ 3 }$

Move the expression to the left-hand side and change its sign

$15+\frac{ x }{ 3 }=1$

Move the constant to the right-hand side and change its sign

$\frac{ x }{ 3 }=1-15$

Calculate the difference

$\frac{ x }{ 3 }=-14$

Multiply both sides of the equation by $3$

$x=-42$