Respuesta :

snog

Answer:

43

Step-by-step explanation:

Let's call this number x. The word sum means addition, so we can write x + 21 = 64. When we subtract 21 from both sides, we get x = 43. Hope this helps!

mberisso

Answer:

the number equals 43

Step-by-step explanation:

We can write the sentence in mathematical terms to get a formula, using "x" for the unknown:

x + 21 = 64

Then we solve for x by subtracting 21 from oth sides of the equation:

x = 64 - 21

x = 43