So, you need to have same ammount of atoms on the left and on the right side of the equation. You need to count the ammount of attoms of every substance on the left, and make sure that on the right side the ammount is same. For example in the 1st one it’s 6Sn+2P4=2Sn3P4, so that you have 6atoms of Sn on the left and 6 atoms of Sn on the right, same with the P
That is called condensation
It has a double C=C bond so that means it's unsaturated, but it can also be a cyclic compound with only simple C-C bonds
MAg*cAg*(T1-T)=ρalc*Valc*calc*(T-T2)
mAg=?(g)
cAg=0.24J/gC
T1=95
T=23.5
Valc=25.6ml
ρalc=0.7893g/ml
T2=19.27
use wollframalpha or calculator
Actually mass and weight are two different things but most people did not understand the difference between them. And they are used synonymously on the earth. Mass is the measure of the amount of matter and weight is the measure of how the force of gravity acts on the mass that is Weight = mass x force of gravity. And they are also directly proportional to each other that is also the reason both terms are used synonymously.