Verified answer

54у - 36у - 9 = 153                   (15i - 21) * 3 + 27 = 234

18у = 153 + 9                             45i - 63 + 27 = 234

18у = 162                                   45i - 36 = 234

у = 162 : 18                                45i = 234 + 36 = 270

у = 9                                           i = 270 : 45       

                                                   i = 6                                                    

(36t + 98) : 14 = 25                   (12u + 30u + 42) : 6 = 21

36t + 98 = 25 * 14                     12u + 30u + 42 = 21 * 6

36t = 350 - 98                            42u + 42 = 126

36t = 252                                   42u = 126 - 42 = 84

t = 252 : 36                                u = 84 : 42

t = 7                                           u = 2