According to the meaning of the question, Shanwa's mobile phone chain is X yuan, Shanwa's key chain is Y yuan and Shanwa's doll is Z yuan.

In the first week, 700 Shanwa mobile phone chains, 1 100 Shanwa key chains and 1500 Shanwa dolls were sold, with a revenue of 70,000 yuan. In the second week, we sold 500 Shanwa mobile phone chains, 800 Shanwa key chains and 1 1000 Shanwa.

There are 700x+1100y+1500z = 70000①.

500 x+800y+ 1 100 z = 5 1000②

500x+500y+500z=t (parameter) ③

From ① 7x+11y+15z = 700④

5x+8y+ 1 1z = 5 10⑤

Then just find the value of x+y+z y+z.

So let x and y be variables and z be constant.

There are 7x+11y = 700-15z.

5x+8y = 5 10- 1 1z

35x+55y=3500-75z

35x+56y=3570-77z

Subtract two expressions

y=70-2z

Incorporate y into the rule

5x+8×(70-2z)= 5 10- 1 1z

5x=-50+5z

x=- 10+z

So x+y+z=- 10+z+70-2z+z=60.

So 500 x+500 y+500 z = 60 x 500 = 30,000 yuan.

That is, the income in the third week is 30,000 yuan.

By the way, help me see if there is any mistake.