We will have the following:

So, the simplification is equal to 1.1.
***Explanation***
![\frac{2.5\operatorname{\ast}2.5\operatorname{\ast}2.5-1.4\operatorname{\ast}1.4\operatorname{\ast}1.4}{(2.5)^2+2.5\operatorname{\ast}1.4+(1.4)^2}]()
First, we multiply all the values that are asked to be multiplied, and we also operate all the exponents. [We recall that a value at the power of a number is the number of times the value is multiplied by itself], then we get that:
![\frac{2.5\ast2.5\operatorname{\ast}2.5-1.4\operatorname{\ast}1.4\operatorname{\ast}1.4}{(2.5\ast2.5)+2.5\operatorname{\ast}1.4+(1.4\ast1.4)}=(15.625-2.744)/(6.25+3.5+1.96)]()
Finally we operate the simpler and lower in the hierarchy of operations expressions: