Evaluate the expression below for s=2 and t=7 3st²-s²

Please help

First replace the letters with the numbers it gave so you have 3(2)(7)^2-(2)^2

multiply the 3 and 2 together to make 6(7)^2-(2)^2

do seven to the second power (7x7) so you get 6(49)-(2)^2

-(2)^2 is the same as -1(2)^2, so that can just become -2^2. so you now have 6(49)-2^2

multiply 6x49 so you have 294-2^2

do two to the second power (2x2) so you get 294-4

294-4=290