for these you need to rearrange the equations and do substitutions.
#3 = if x+y=5 then you know x = 5-y
now substitute that equation for x in the 2nd one so x + 2y = 8 becomes
5-y + 2y = 8 2y - y becomes 1y which becomes y then subtract 5 from each side to get y =3
now replace y with 3 in the first equation x = 5-3 so x = 2
so (2,3) is the answer
same type of work for #4
2x-y=6 ,S0 y = 2X+6
so now you have 4x+2(2x+6)=-4
that becomes 4x +4x+12 = -4
8x+8 = 1, x =1
y = 2(1)-6 = -4
so answer is (1,-4)
There are 4 people in total
(including herself)
so 36 smarties should be evenly distributed among 4 people
so answer = 36/4 = 9
35 + 52 + 3(x + 2) = 180
87 + 3x + 6 = 180 ( add the like terms and use distributive property)
93 + 3x = 180
-93 -93
3x = 87
÷3 ÷3
x = 29
( the sum of all triangle angles is 180)