The difference between two number is 18 if four times the second number is less then three what is the sum these two number?

Let first number = P
And second number = Q
According to the question
P - Q = 10 ....(i)
And 3P - 4Q = 18...(ii)
on multiply eq (i) by 3 and then subtract eq (ii) from it
3P - 3Q = 54
3P - 4Q = 18
Q = 36
On putting the value of Q in the eq (i)
P = 18 + Q = 18 +36
⇒ P = 54
Required sum = P + Q = 54 +36 =90