Answer:

3(C + 5) = 7

Step-by-step explanation:

Let C = unknown number

The sum of a number and 5:

C + 5

Three times the sum of a number and 5:

3(C + 5)

Three times the sum of a number and 5 is 7:

3(C + 5) = 7

To solve

Use the distributive law:  a(b + c) = ab + ac

⇒ 3C + 15 = 7

Subtract 15 from both sides:

⇒ 3C = -8

Divide both sides by 3:

⇒ C = -8/3

• Le the number be c

• Sum of a number and c means c+5
• 3times that means 3(c+5)

So

The expression is

• 3(c+5)=7

On solving

• 3c+15=7
• 3c=-8
• c=-8/3