The number sentence 4x7=(4x3)+(4x4) is an example of what property

The number sentence 4x7=(4x3)+(4x4) is an example of distributive property. 
The distributive property states the following:
a × (b + c) = a × b + a × c
Multiplying a sum by a number is the same as multiplying each addend by the number and then adding the products. 
In our case, a=4 b+c=7, b=3, c=4

Arhombus is a quadrilateral.

It's like discovering the answer to a puzzle. the purpose in solving an equation is to find the value or values of the variable that makes it a true statement. any value of the variable that makes the equation true is called a solution to the equation.