How to add new columns (new calculation) using R STUDIO?

I’ll generate one data. Let’s say this is a math and english score for 8 students from different countries.

name=c("Jack","Kate","John","Jane","David","Min","Hyuk","Jisoo")
math=c(100,85,95,75,80,90,90,85)
eng=c(50,90,90,88,95,85,87,88)
country=c("USA","Spain","France","Germany","Netherlands", rep("Korea",3))
gender=c(rep(c("Male","Female"),times=4))
enroll=c(rep(c("Yes","No"),each=4))
grade=data.frame(name,math,eng,country,gender,enroll)

print(grade)
   name math eng     country gender enroll
1  Jack  100  50         USA   Male    Yes
2  Kate   85  90       Spain Female    Yes
3  John   95  90      France   Male    Yes
4  Jane   75  88     Germany Female    Yes
5 David   80  95 Netherlands   Male     No
6   Min   90  85       Korea Female     No
7  Hyuk   90  87       Korea   Male     No
8 Jisoo   85  88       Korea Female     No

I would like to adjust the scores by giving more weight to math. Since math was particularly difficult, I will increase the weight given to math.

grade$final= (grade$math*1.5 + grade$eng)/2

print(grade)
   name math eng     country gender enroll  final
1  Jack  100  50         USA   Male    Yes 100.00
2  Kate   85  90       Spain Female    Yes 108.75
3  John   95  90      France   Male    Yes 116.25
4  Jane   75  88     Germany Female    Yes 100.25
5 David   80  95 Netherlands   Male     No 107.50
6   Min   90  85       Korea Female     No 110.00
7  Hyuk   90  87       Korea   Male     No 111.00
8 Jisoo   85  88       Korea Female     No 107.75

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