Hint: Here we will explain that the given number is composite. Firstly we will solve the given value and get a single number. Then we will write down the factor of the value we got and check how many factors are there. Finally we will prove our statement.
Complete step-by-step answer: We have to explain that $3 \times 5 \times 7 + 7$ is a composite number. So, firstly we will solve the given value by using the operation used in it. $ 3 \times 5 \times 7 + 7 \\ \Rightarrow 105 + 7 \\ \Rightarrow 112 \\ $ Now, we will write the factors of the value obtain as, $112 = 2 \times 2 \times 2 \times 2 \times 7 \times 1$ So we have more than one factor of 112 so it is a composite number. We can also see that 112 is an even number so it is definitely a composite number.
Note: Arithmetic operations are used to calculate the values in an algebraic equation. Composite number is an integer that can be formed by multiplying two small positive integers. Composite numbers have other factors other than 1 and themselves. We can write every composite number as a product of two or more prime numbers; this is also known as the theorem of arithmetic. The type of composite numbers depends on the number of prime factors of it. A composite number having two prime factors is known as semi-prime or 2-almost prime numbers. A composite number with three distinct prime factors is known as sphenic number. All composite numbers have at least three factors it can have more also. Another name for composite numbers is rectangular numbers.