How to solve the equation of 2.8 × 4 + 5x = 15.8

How to solve the equation of 2.8 × 4 + 5x = 15.8

11.2+5x=15.8
5x=15.8-11.2
5x=4.6
x=0.92

How to solve the equation of 5x + 8y = 161?

Infinite sister

How to solve the system of equations {x + y + Z = 14, 5x + 8y + 10z = 120? List the detailed process, preferably the solution of grade one
Question: in order to save freight, Wenzhou municipal government plans to use three types of vehicles (a, B and C) to participate in the transportation at the same time. It is known that the total number of vehicles is 14. Can you find out the number of vehicles of the three types? How much is the freight at this time?
Supplement: drought relief materials need 120 tons!
Model a, B and C
Vehicle carrying capacity (T / vehicle) 58 10
Vehicle freight (yuan / vehicle) 400 500 600
List equations and borrow them! The process should be detailed! I am a junior one student

Suppose: there are x vehicles for vehicle a, y vehicles for vehicle B, and 14-x-y vehicles for vehicle C
Formula: 5 * x + 8 * y + 10 * (14-x-y) = 120
Y = 10-2.5 * x
400*x+500*y+600*(14-x-y)
=50*x+2900
The minimum freight is required, and three kinds of vehicles participate in the transportation at the same time
x=1；
y=8;
z=5;
Freight: 7400

Using the knowledge of higher numbers to solve the plane square of the straight line (X-2) / 5 = (y + 1) / 2 = (Z-2) / 4 and perpendicular to the plane x + 4y-3z + 1 = 0

Straight line passing through point (2, - 1,2)
The direction vector of the straight line is: (5,2,4) (of course, it can be put over)
The normal vector of a plane is (1,4, - 3), and the normal vector of a plane and the normal vector of a straight line are cross multiplied (outer product) to get the plane
Then we use the formula (X-2) e1 + (y + 1) E2 + (Z-2) E3 = 0 to get the plane, where (E1, E2, E3) is r