An element called X consists of four isotopes A, B, C and D. Their relative atomic masses are 67.0, 68.0, 66.0 and 64.0, respectively. The relative ratios of A, B and C are 1: 4: 7, respectively. If the relative atomic mass of the element is 65.4, calculate the relative abundance of the four isotopes??? please help me​

I’m an electrically neutral atomic any element, there are equal numbers of

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt

Which of the following is not an assumption that scientists must make about the natural world? a. regularity b. causality c. predictability d. plausibility