Solve the system:
x + y = 19
y = 3x - 1

This is a simultaneous equation, and you can solve it using the substitution method. You can put the values for y into the first equation.

Therefore: x + (3x - 1) = 19

We can simplify this equation: 4x - 1 = 19

Next, we have to make 4x on its own, and so add 1 to both sides: 4x = 20.

To find x on its own, we have to divide both sides by 4: x = 5

To find the value of y, you can substitute the value of x that we just found out into the second equation: y = 3 x 5 - 1

Simplify: y = 14

Therefore, x = 5, and y = 14

1. 0.3 •4 is the same as 4 groups of 0.32. 7•0.8 is the same as 7 groups of 0.83. it increases by 0.5 every time, so 0.5x4 it increases by 0.9 every time, so 0.9x5. 0.9•12=10.86. 0.47•5=2.35i can finish the next ones in a separate post