y=20 and x=12 what is the constant of proportionality

step-by-step explanation:

ok so im not 100% sure but you would start by adding 5.1t and 1.9t beacuse they have the same variable. that is 7t.   then add -3.6 + 1.2 which is -2.4

so then keep that as -2.4 + 7t. i apologize if this is incorrect. best luck on your test < 3

51

step-by-step explanation:

73-22=51 the   mass number minus the amount of protons gives you the amount of neutrons