Currently studying mathematics for engineers third edition given i havnt done maths for about 9 years its not going to bad but im stuck on theses question

The pressure in a vessel is increased by 12% to 130 nm calculate the original pressure now this is how i worked it out can someone please tell me where im going wrong

12/ 100= 0.12x130= 15.6 this answer being the increase thus giving me 130- 15.6 =114.4 ( original value)

But the answer in the book gives 116.07 where am i going wrong ?

Next question

Express the ratio 1 1/2 : 3 1/4 using only integers now this one i cannot figure out an integer is a whole number so how would i calculate this ?

Any help appreciated