Which properties change the composition of a substance? physical properties

chemical properties

chemical and physical properties

neither chemical nor physical properties

Only chemical properties change the composition of a substance,

Physical properties do not change composition. Physical properties have to do with the physical appearance of an object.

Chemical properties can be observed during a chemical reaction. For instance when paper is being burnt. Chemical changes are what causes a substance to change into a different substance entirely.

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the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69