My friend Tony is an American 1. He is ten years old. He lives2 his family in China now. There are 3  people in his family; his mother Mrs. Green, his father Mr. Green and his little sister Amy. He has a white cat. 4 name is Betty. Look！Amy is playing 5Betty. His father, Mr. Green, is watc­hing TV. His mother is doing housework. What about Tony? He is doing 6 Chinese homework. He can't 7Chinese well, but he likes Chinese very much. Tony's 8 works in a TV station. His father works in a school as an 9 teacher. Tony and his sister 10 to the same school.

已知函数$f\left(x\right)=\cos x,x\in \left(0,2\mathrm{\pi }\right)$有两个不同的零点$x_1,x_2$，且方程$f\left(x\right)=m$有两个不同的实根$x_3,x_4$.若把这四个数按从小到大排列构成等差数列，则实数$m$的值为

x÷60－60=420

x=____