The sum of 42 & a number n is equal to 51

Translate the phrase into a mathematical equation.

"The sun of 42 and a number ... " this phrase denotes that addition is being done on two numbers, 42 and a number. "a number" can be translated into a variable.

" ... is equal to 51" so the whole expression equals 51

Now we have our equation: 42 + x = 51

Solve for x.

42 + x = 51

x = 9

So, x is equal to 9.