-5(x -6) = 10x . . . . . given
-5x +30 = 10x . . . . distributive property of multiplication over addition
30 = 15x . . . . . . . . addition property of equality (5x was added to both sides)
2 = x . . . . . . . . . . . division property of equality (both sides were divided by 15)
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There is a "property of equality" for any operation you want to do to both sides of the equation: addition, subtraction, multiplication, division, application of a function (such as log or square root or any trig function, for example).
The distributive property lets you add or remove parenthenses according to its rules.
Identity properties of addition and multiplication allow you to add 0 or multiply by 1 anywhere anytime. These operations can take any useful form, such as "completing the square" of a quadratic (by adding and subtracting the same number), changing units [(1 h)/(60 min) = 1, for example], or finding percentages (multiplying by 100%).