Can someone solve this, quite difficult simultaneous equation:

2y + z = 13
2x + z = 11
x + y + z=12

Amonument at a park is in the shape of a right square pyramid. a diagram of the pyramid and its net are shown. what is the surface area of the monument? enter the answer in the box. m²

Zoe placed colored blocks on a scale in science class. each block weighed 0.8 ounces. the total weight of all the colored blocks was 12.8 ounces. how many blocks did zoe place on the scale? write and solve an equation to find the answer.

What is the perimeter of square abcd? units units 28 units 37 units