maybe multiply 2 to each side to eliminate the fraction. so 3x+15<60. subtract 15 to isolate the variable term so 3x<45. divide by 3 to isolate x so x<15. check the work. is the inequality true for all values of x less than 15? let's try the first possible integer value, 14, to be sure. 3(14)+15= 57. so 57/2<30. now 57/2 is 28.5 and 28.5<30 so it seems right
You would put these in a fraction then cross multiply so 15/1800 and 3/x then you get 5400 equals 15x then divide by 15 on both sides to get x equals 360