The sum of half a number and 49 is 9/2 of the number
Substitute x for the words "a number" and "the number".
The sum of half x and 49 is 9/2 of x
Substitute
for "half x"
The sum of
and 49 is 9/2 of x
Substitute
for the words "9/2 of x"
The sum of
and 49 is 
Substitute
for the words "The sum of
and 49"
is 
Substitute an equal sign " = " for the word "is":



Subtract
from both sides:






Divide both sides by 4


Edwin